Multi-stage polymeric latexes, coating compositions containing such latexes, and articles coated therewith

ABSTRACT

An aqueous coating composition useful in coating a variety of substrates, including interior or exterior portions of food or beverage cans. The coating composition includes a multi-stage polymeric latex having two or more emulsion polymerized stages in an aqueous carrier liquid, wherein the latex has one or both of:(i) a lower glass transition temperature (Tg) emulsion polymerized stage having a calculated Tg that is at least 20° C. lower than a calculated Tg of a higher Tg emulsion polymerized stage, or(ii) a gradient Tg with at least a 20° C. differential in the calculated Tg of monomers fed at the start of polymerization compared to monomers fed at the end of polymerization.When spray-applied on the interior of a food or beverage can, the composition exhibits a global extraction result of less than 50 ppm and a metal exposure value of less than 3 mA.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation under 35 U.S.C. § 111(a) ofInternational Application No. PCT/US2018/049059 filed on Aug. 31, 2018,which claims priority to U.S. Provisional Application No. 62/553,309filed on Sep. 1, 2017 and U.S. Provisional Application No. 62/725,196filed on Aug. 30, 2018, both of which are entitled “MULTI-STAGEPOLYMERIC LATEXES, COATING COMPOSITIONS CONTAINING SUCH LATEXES, ANDARTICLES COATED THEREWITH” and the disclosures of both of which areincorporated herein by reference in their entirety.

BACKGROUND

Bisphenol A has been used to prepare polymers having a variety ofproperties and uses. For example, bisphenol A may be reacted withepichlorohydrin to provide polymers useful in packaging coatings. Thereis a desire to reduce or eliminate the use of certain bisphenolA-derived polymers in food or beverage container coatings. Although anumber of replacement coating compositions made without bisphenol A havebeen proposed, some replacement compositions have exhibited insufficientcoating properties such as insufficient corrosion resistance on metalsubstrates, insufficient flexibility or insufficient toughness.

The balance of coating performance attributes required for a coatingcomposition to be suitable for use as a food or beverage can coatingsare particularly stringent and are unique from other coating end uses.As such, coatings designed for other ends uses are not typicallysuitable for use as food or beverage can coatings.

For example, coatings for use on food or beverage containers shouldavoid unsuitably altering the taste of the packaged food or beverageproducts, and should also avoid flaking or chipping into the packagedproducts. The coatings should also resist chemically aggressive food orbeverage products (which can have a complex chemical profile, includingsalt, acids, sugars, fats, etc.) for extended periods of time (e.g.,years). Food or beverage container coatings should also have goodadhesion to the underlying substrate and remain sufficiently flexibleafter curing, because subsequent fabrication and denting duringtransportation, storage or use (e.g., by dropping) may cause the metalsubstrate to deform, which will cause the coating to flex. A brittlecoating will crack during flexure, exposing the container metal to thepackaged products, which can sometimes cause a leak in the container.Even a low probability of coating failure may cause a significant numberof containers to leak, given the high number of food and beveragecontainers produced.

Accordingly, it will be appreciated that what is needed in the art areimproved coating compositions that are made without intentionally usingbisphenol A, but which exhibit the stringent balance of coatingproperties to permit the use of such coating compositions on food orbeverage containers.

SUMMARY

In one aspect, the present invention provides an aqueous coatingcomposition comprising a multi-stage polymeric latex having two or moreemulsion polymerized stages in an aqueous carrier liquid, wherein thelatex has one or both of:

-   -   (i) a lower glass transition temperature (“Tg”) emulsion        polymerized stage having a calculated Tg that is at least 20° C.        lower than a calculated Tg of a higher Tg emulsion polymerized        stage, or    -   (ii) a gradient Tg with at least a 20° C. differential in the        calculated Tg of monomers fed at the start of polymerization        compared to monomers fed at the end of polymerization; and    -   wherein when spray applied onto an interior of a 355 mL (12 U.S.        fluid oz.) no. 211 two-piece drawn and ironed aluminum beverage        can at 115 milligrams per can coating weight and cured at        188° C. to 199° C. (measured at the can dome) for 55 seconds,        the cured coating composition exhibits:    -   (iii) a global extraction result of less than 50 ppm; and    -   (iv) a metal exposure of less than 3 mA on average when the can        is filled with 1% NaCl in deionized water and tested pursuant to        the Initial Metal Exposure test method disclosed herein.

In another aspect, the present invention provides an article that hasbeen or will be formed into a food or beverage container or containercomponent, the article comprising a metal substrate having on at leastone surface a coating formed from an aqueous coating compositioncomprising:

-   -   a multi-stage polymeric latex having two or more emulsion        polymerized stages in an aqueous carrier liquid, wherein the        latex has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization; and    -   wherein when spray applied onto an interior of a 355 mL (12 U.S.        fluid oz.) no. 211 two-piece drawn and ironed aluminum beverage        can at 115 milligrams per can coating weight and cured at        188° C. to 199° C. (measured at the can dome) for 55 seconds,        the cured coating composition exhibits:        -   (iii) a global extraction result of less than 50 ppm; and        -   (iv) a metal exposure of less than 3 mA on average when the            can is filled with 1% NaCl in deionized water and tested            pursuant to the Initial Metal Exposure test method disclosed            herein.

In another aspect, the present invention provides a method for making acoated food or beverage container or container component, the methodcomprising the steps of:

-   -   (a) spray applying on an interior surface of a metal food or        beverage can having a body portion and an end portion an aqueous        coating composition comprising a multi-stage polymeric latex        having two or more emulsion polymerized stages in an aqueous        carrier liquid, wherein the latex has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization; and    -   (b) curing the coating composition to form a hardened coating;    -   wherein the hardened coating exhibits:        -   (iii) a global extraction result of less than 50 ppm; and        -   (iv) a metal exposure of less than 3 mA on average when the            can is filled with 1% NaCl in deionized water and tested            pursuant to the Initial Metal Exposure test method disclosed            herein.

In another aspect, the present invention provides a method for making acoated food or beverage container or container component, the methodcomprising the steps of:

-   -   (a) applying to at least one metal substrate surface of a food        or beverage container or container component a coating formed        from an aqueous coating composition comprising a multi-stage        polymeric latex having two or more emulsion polymerized stages        in an aqueous carrier liquid, wherein the latex has one or both        of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization; and    -   (b) curing the coating composition to form a hardened coating;    -   wherein the cured coating composition:        -   (iii) exhibits a global extraction result of less than 50            ppm; and        -   (iv) has a dry coating weight of about 0.6 grams per square            meter (“gsm”) to about 13 gsm.

In another aspect, the present invention provides an aqueous coatingcomposition comprising:

-   -   a resin system including a water-dispersible polymer and two or        more emulsion polymerized stages of a multi-stage polymeric        latex in an aqueous carrier liquid, wherein the        water-dispersible polymer is incorporated into the multi-stage        polymeric latex, blended with the multi-stage polymeric latex,        or both; and wherein the latex has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization.

In another aspect, the present invention provides an article that hasbeen or will be formed into a food or beverage container or containercomponent, the article comprising a metal substrate having on at leastone surface a coating formed from an aqueous coating compositioncomprising:

-   -   a resin system including a water-dispersible polymer and two or        more emulsion polymerized stages of a multi-stage polymeric        latex in an aqueous carrier liquid, wherein the        water-dispersible polymer is incorporated into the multi-stage        polymeric latex, blended with the multi-stage polymeric latex,        or both; and wherein the latex has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization.

In another aspect, the present invention provides a method for making alatex dispersion useful for coating food or beverage containers orcontainer components, the method comprising the steps of:

-   -   (a) providing an aqueous dispersion of a water-dispersible        polymer; and    -   (b) emulsion polymerizing two or more stages in the presence of        the aqueous dispersion to form a multi-stage polymeric latex,        wherein the latex has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization.

In another aspect, the present invention provides a method for making acoated food or beverage container or container component, the methodcomprising the steps of:

-   -   (a) spray-applying on an interior surface of a metal food or        beverage can having a body portion and an end portion an aqueous        coating composition comprising a resin system including a        water-dispersible polymer and two or more emulsion polymerized        stages of a multi-stage polymeric latex in an aqueous carrier        liquid, wherein the water-dispersible polymer is incorporated        into the multi-stage polymeric latex, blended with the        multi-stage polymeric latex, or both; and wherein the latex has        one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization; and    -   (b) curing the coating composition to form a hardened coating.

In another aspect, the present invention provides a method for making acoated food or beverage container or container component, the methodcomprising the steps of:

-   -   (a) applying to at least one metal substrate surface of a food        or beverage container or container component a coating formed        from an aqueous coating composition comprising a resin system        including a water-dispersible polymer and two or more emulsion        polymerized stages of a multi-stage polymeric latex in an        aqueous carrier liquid, wherein the water-dispersible polymer is        incorporated into the multi-stage polymeric latex, blended with        the multi-stage polymeric latex, or both; and wherein the latex        has one or both of:        -   (i) a lower Tg emulsion polymerized stage having a            calculated Tg that is at least 20° C. lower than a            calculated Tg of a higher Tg emulsion polymerized stage, or        -   (ii) a gradient Tg with at least a 20° C. differential in            the calculated Tg of monomers fed at the start of            polymerization compared to monomers fed at the end of            polymerization; and    -   (b) curing the coating composition to form a hardened coating.

In another aspect, the present invention provides an aqueous dispersionthat includes a multi-stage polymeric latex having two or more emulsionpolymerized stages and is suitable for use in forming a food-contactcoating on a metal substrate of a food or beverage can. The latex hasone or both of: (i) a “lower” Tg emulsion polymerized stage having acalculated Tg that is at least 20° C., at least 30° C., at least 35° C.,at least 40° C., at least 50° C., at least 60° C., or at least 70° C.lower than a calculated Tg of a “higher” Tg emulsion polymerized stageor (ii) a gradient Tg with at least a 20° C. differential in thecalculated Tg of monomers fed at the start of polymerization compared tomonomers fed at the end of polymerization. In some embodiments, themulti-stage polymeric latex is present in a resin system that includes awater-dispersible polymer (e.g., an acrylic polymer, a polyetherpolymer, a polyolefin polymer, a polyester polymer, a polyurethanepolymer, or a mixture or copolymer thereof), wherein thewater-dispersible polymer is incorporated into the multi-stage polymericlatex, blended with the multi-stage polymeric latex, or both.

In some embodiments, the above-mentioned aqueous coating compositioncomprises an aqueous carrier liquid and a resin system comprising amulti-stage polymeric latex having two or more emulsion polymerizedstages dispersed in the aqueous carrier, wherein the latex has one orboth of: (i) a lower Tg emulsion polymerized stage having a calculatedTg that is at least 20° C., at least 30° C., at least 35° C., at least40° C., at least 50° C., at least 60° C., or at least 70° C. lower thana calculated Tg of a higher Tg emulsion polymerized stage or (ii) agradient Tg with at least a 20° C. differential in the calculated Tg ofmonomers fed at the start of polymerization compared to monomers fed atthe end of polymerization. In some embodiments, if the latex has theabove (i), then more than 50 weight percent of the emulsion polymerizedstages preferably have a calculated Tg of at least 40° C., at least 50°C., at least 60° C., at least 70° C., or at least 80° C.

In some embodiments, the above-mentioned aqueous coating compositioncomprises an aqueous carrier liquid and a resin system that includes awater-dispersible polymer and two or more emulsion polymerized stages ofa multi-stage polymeric latex. The water-dispersible polymer ispreferably incorporated into the multi-stage polymeric latex, blendedwith the multi-stage polymeric latex, or both. The latex preferably hasone or both of: (i) a lower Tg emulsion polymerized stage having acalculated Tg that is at least 20° C., at least 30° C., at least 35° C.,at least 40° C., at least 50° C., at least 60° C., or at least 70° C.lower than a calculated Tg of a higher Tg emulsion polymerized stage or(ii) a gradient Tg with at least a 20° C. differential in the calculatedTg of monomers fed at the start of polymerization compared to monomersfed at the end of polymerization.

In some embodiments, at least one monomer A of the below Formula (I) isemployed to prepare one or more of the emulsion polymerized stages:CH₂═C(R¹)—X_(n)—C(CH₃)_(t)(R²)_(3-t)  (I)wherein:

-   -   R¹ is hydrogen or an alkyl group, more typically hydrogen or a        methyl group;    -   n is 0 or 1, more typically 1;    -   X, if present, is a divalent linking group; more typically an        amide, carbonate, ester, ether, urea, or urethane linkage; and        even more typically an ester linkage of either directionality        (viz., —C(O)—O— or —O—C(O)—);    -   t is 0 to 3;    -   each R², if present, is independently an organic group that may        optionally be itself branched, more typically an alkyl group        that may optionally include one or more heteroatoms (e.g., N, O,        P, Si, etc.); and    -   two or more R² may optionally form a cyclic group with one        another.

In some embodiments, at least one (meth)acrylate of the below Formula(II) is employed to prepare one or more of the emulsion polymerizedstages:CH₂═C(R³)—CO—OR⁴  (II)wherein:

-   -   R³ is hydrogen or methyl, and    -   R⁴ is an alkyl group preferably containing one to sixteen carbon        atoms, a cycloaliphatic group, an aryl group, a silane group, or        a combination thereof.

In some embodiments, the above-mentioned aqueous coating compositioncomprises an aqueous carrier liquid and a resin system that includes s amulti-stage polymeric latex having two or more emulsion polymerizedstages, wherein the multi-stage latex is formed by emulsion polymerizingethylenically unsaturated monomers in the presence of an aqueousdispersion of a water-dispersible polymer. The latex preferably has oneor both of: (i) a lower Tg emulsion polymerized stage having acalculated Tg that is at least 20° C., at least 30° C., at least 35° C.,at least 40° C., at least 50° C., at least 60° C., or at least 70° C.lower than a calculated Tg of a higher Tg emulsion polymerized stage or(ii) a gradient Tg with at least a 20° C. differential in the calculatedTg of monomers fed at the start of polymerization compared to monomersfed at the end of polymerization. The water-dispersible polymerpreferably comprises a polyether polymer.

In some embodiments, the above-mentioned aqueous coating compositioncomprises an aqueous carrier liquid and a resin system that includes amulti-stage polymeric latex formed by emulsion polymerizingethylenically unsaturated monomers in two or more stages (e.g., a lowerTg stage and a higher Tg stage) in the presence of a water-dispersiblepolymer (e.g., an acrylic polymer, a polyether polymer, a polyolefinpolymer, a polyester polymer, a polyurethane polymer, or a mixture orcopolymer thereof), wherein the emulsion polymerized ethylenicallyunsaturated monomers comprise at least 80 wt. % of two or more (e.g.,two, three, four, or five) of methyl methacrylate, ethyl acrylate, ethylmethacrylate, butyl acrylate (e.g., n-butyl acrylate), and butylmethacrylate (e.g., n-butyl methacrylate).

In some embodiments, the above-mentioned coating compositions containless than about 10 wt. %, less than about 5 wt. %, less than about 1 wt.% or do not contain polyether compounds or polymers. In someembodiments, the above-mentioned coating compositions are substantiallyfree of or do not contain each of bisphenol A, bisphenol F, andbisphenol S. In some embodiments, the above-mentioned coatingcompositions are optionally substantially free of or do not containstyrene.

In yet another aspect, substrates (e.g., metal substrates) having one ormore of the above-mentioned coating compositions disposed thereon arealso disclosed. In some embodiments, the substrate is a metal food orbeverage can or container, or portion thereof (e.g., twist-off closurelid, can end, beverage can end, can sidewall body portion and bottom endportion, etc.) with the disclosed coating composition invention appliedon an exterior surface, an interior surface, or a combination of both.Certain embodiments of the coating composition of the present inventionhave been found to be particularly suitable for spray application on theinterior of food or beverage cans, including, e.g., aluminum beveragecans.

In yet another aspect, the present invention provides a method ofcoating a food or beverage can. The method preferably includes applying(e.g., spray applying, roll coating, etc.) one or more of theabove-mentioned coating compositions to a surface of a metal substrateprior to or after forming the metal substrate into a food or beveragecan or a portion thereof.

In yet another aspect, the present invention provides food contactmulti-stage latex dispersions and methods of making food contactmulti-stage latex dispersions. In preferred embodiments, the methodincludes providing an aqueous dispersion of a water-dispersible polymer(e.g., an acrylic polymer, a polyether polymer, a polyolefin polymer, apolyester polymer, a polyurethane polymer, or a mixture or copolymerthereof); and emulsion polymerizing two or more latex stages in thepresence of the aqueous dispersion to form a multi-stage polymericlatex, wherein the latex has one or both of: (i) a lower Tg emulsionpolymerized stage having a calculated Tg that is preferably at least 20°C., at least 30° C., at least 35° C., at least 40° C., at least 50° C.,at least 60° C., or at least 70° C. lower than a calculated Tg of ahigher Tg emulsion polymerized stage or (ii) a gradient Tg with at leasta 20° C. differential in the calculated Tg of monomers fed at the startof polymerization compared to monomers fed at the end of polymerization.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which can be used invarious combinations. In each instance, the recited list serves only asa representative group and should not be interpreted as limiting or asan exclusive list.

The details of one or more additional embodiments of the invention areset forth in the description below. Other features, objects, andadvantages of the invention will be apparent from the description andfrom the embodiments.

Selected Definitions

Unless otherwise specified, the following terms as used herein have themeanings as provided below.

The terms “a,” “an,” “the,” “at least one,” and “one or more” are usedinterchangeably. Thus, for example, a coating composition that comprises“a” polyether polymer means that the coating composition includes “oneor more” polyether polymers.

The terms “acrylate” and “acrylic” are used broadly herein andencompasses materials prepared from, for example, one or more of acrylicacid, methacrylic acid, or any acrylate or methacrylate compound. Thus,for example, a polyether-acrylate copolymer in which the “acrylate”component consists entirely of polymerized (meth)acrylic acid wouldstill include an “acrylate” component even though no (meth)acrylatemonomer was employed.

The term “bisphenol” refers to a polyhydric polyphenol monomer havingtwo phenylene groups that each have a hydroxyl group attached to acarbon atom of the ring, wherein the rings of the two phenylene groupsdo not share any atoms in common.

The terms “comprises”, “comprising” and variations thereof do not have alimiting meaning where these terms appear in the description andembodiments.

The term “dihydric monophenol” refers to a polyhydric monophenol thatonly includes two hydroxyl groups attached to the aryl or heteroarylring.

The term “diphenol” refers to a polyphenol in which two phenylene groupseach have one hydroxyl group.

The term “easy open end” refers to a can end (typically an end of a foodor beverage can) that includes (i) a frangible opening portion (whichfor some beverage can ends functions as a drinking spout) and (ii) ariveted portion for attaching a pull tab thereto for purposes of openingthe frangible opening portion to access a product housed within a can.

The terms “estrogenic activity” or “estrogenic agonist activity” referto the ability of a compound to mimic hormone-like activity throughinteraction with an endogenous estrogen receptor, typically anendogenous human estrogen receptor.

The term “flavor scalping” refers to a loss of quality in a packageditem due either to its aroma or other flavor components being absorbedby the packaging (e.g., an interior beverage can coating) or due to afood or beverage contained in the packaging absorbing undesirable aromasor other flavor components from the packaging, such as may arise due tocoating film failure.

The term “food-contact surface” refers to a surface of an article (e.g.,a food or beverage container) that is in contact with, or suitable forcontact with, a food or beverage product.

The term “incorporated”, when used with respect to a water-dispersiblepolymer incorporated into a latex polymer or particle, means that thewater-dispersible polymer is physically entangled, imbibed into orcovalently bound with the polymer particles of the latex such that thewater-dispersible polymer and latex cannot readily be separated usingtechniques such as washing or separation.

A group that may be the same or different is referred to as being“independently” something. The term “group” also encompasses single atommoieties. Thus, for example, a halogen atom can be a group.

The term “low molecular weight” refers to a material, generallymonomeric or oligomeric in nature, having a molecular weight less thanabout 2,000 or less than about 1,000. In the case of oligomericmaterials containing molecules having a variety of molecular weights,the term low molecular weight refers to the number average molecularweight.

The term “(meth)” as used in “(meth)acrylate” and “(meth)acrylic acid”is intended to indicate that either a hydrogen or methyl group may beattached to the pertinent carbon atom of the monomer. For example “ethyl(meth)acrylate” encompasses both ethyl acrylate, ethyl methacrylate, andmixtures thereof.

The term “multi-stage” when used with respect to a latex polymer meansthe polymer was made using discrete charges of two or more monomers,made using a varying (e.g., continuously-varying) charge of two or moremonomers, or made using a combination of both discrete charges andvarying charges of two or more monomers. The presence in an initiallatex polymer reaction mixture of “seed” particles representing no morethan 10 wt. % of the latex polymer solids in the final latex, whether asan inorganic particulate seed (e.g., clay or glass particles), as apreformed particulate polymer seed, or as particulate seed polymerformed in situ, will not be deemed to provide a stage of a multi-stagepolymer or to provide a basis for designating a single stage polymermade using such seed polymer as a multi-stage polymer. The presence in alatex composition of a separate, non-latex polymer, will not be deemedto provide a stage of a multi-stage polymer or to provide a basis fordesignating a single stage polymer made using such separate polymer as amulti-stage polymer.

The term “on,” when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

The term “or” when used with respect to a set of items, choices or otherpossibilities refers to either the inclusive or exclusive selection ofsuch items, choices or other possibilities.

The term “phenylene” refers to a six-carbon atom aryl ring (e.g., as ina benzene group) that can have any substituent groups (including, e.g.,hydrogen atoms, hydrocarbon groups, oxygen atoms, hydroxyl groups,etc.). Thus, for example, the following aryl groups are each phenylenerings: —C₆H₄—, —C₆H₃(CH₃)—, and —C₆H(CH₃)₂(OH)—. In addition, forexample, each of the aryl rings of a naphthalene group are phenylenerings.

The term “polyhydric phenol” (which includes dihydric phenols) refersbroadly to any compound having one or more aryl or heteroaryl groups(more typically one or more phenylene groups) and at least two hydroxylgroups attached to a same or different aryl or heteroaryl ring. Thus,for example, both hydroquinone and 4,4′-biphenol are considered to bepolyhydric phenols. As used herein, polyhydric phenols typically havesix carbon atoms in an aryl ring, although it is contemplated that arylor heteroaryl groups having rings of other sizes may be used.

The term “polyhydric monophenol” refers to a polyhydric phenol that (i)includes an aryl or heteroaryl group (more typically a phenylene group)having at least two hydroxyl groups attached to the aryl or heteroarylring and (ii) does not include any other aryl or heteroaryl rings havinga hydroxyl group attached to the ring.

The term “polyhydric polyphenol” (which includes bisphenols) refers to apolyhydric phenol that includes two or more aryl or heteroaryl groupseach having at least one hydroxyl group attached to the aryl orheteroaryl ring.

The term “polyphenol” refers to a polyhydric material having two or morephenylene groups that each include a six-carbon ring and a hydroxylgroup attached to a carbon atom of the ring, wherein the rings of thephenylene groups do not share any atoms in common.

The term “polymer” includes both homopolymers and copolymers (e.g.,polymers of two or more different monomers). Similarly, unless otherwiseindicated, the use of a term designating a polymer class such as, forexample, “polyether” is intended to include both homopolymers andcopolymers (e.g., polyether-acrylate copolymers).

The terms “preferred” and “preferably” refer to embodiments that mayafford certain benefits, under certain circumstances. However, otherembodiments may also be preferred, under the same or othercircumstances. Furthermore, the recitation of one or more preferredembodiments does not imply that other embodiments are not useful, and isnot intended to exclude other embodiments from the scope of theinvention.

The term “substantially free” when used with respect to a coatingcomposition that may contain a particular compound means that thecoating composition contains less than 1,000 parts per million (ppm) ofthe recited compound (corresponding to less than 0.1 wt. %) regardlessof whether the compound is mobile in the coating or bound to aconstituent of the coating. The term “essentially free” when used withrespect to a coating composition that may contain a particular compoundmeans that the coating composition contains less than 100 parts permillion (ppm) of the recited compound regardless of whether the compoundis mobile in the coating or bound to a constituent of the coating. Theterm “essentially completely free” when used with respect to a coatingcomposition that may contain a particular compound means that thecoating composition contains less than 5 parts per million (ppm) of therecited compound regardless of whether the compound is mobile in thecoating or bound to a constituent of the coating. The term “completelyfree” when used with respect to a coating composition that may contain aparticular compound means that the coating composition contains lessthan 20 parts per billion (ppb) of the recited compound regardless ofwhether the compound is mobile in the coating or bound to a constituentof the coating. When the phrases “free of” (outside the context of theaforementioned phrases), “do not contain”, “does not contain”, “does notinclude any” and the like are used herein, such phrases are not intendedto preclude the presence of trace amounts of the pertinent structure orcompound which may be present but were not intentionally used, e.g., thepresence of environmental contaminants. As will be appreciated bypersons having ordinary skill in the art, the amount of a compound in aningredient, polymer, formulation or other component typically may becalculated based on the amounts of starting materials employed andyields obtained when making such ingredient, polymer, formulation orother component.

The recitations of numerical ranges by endpoints include all numberssubsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 4 to 5, etc.).

DETAILED DESCRIPTION

The present invention relates to a coating composition that includes amulti-stage polymeric latex, which is particularly suitable for use informulating packaging coatings, and particularly food or beverage cancoatings. The coating composition of the present invention is preferablyan aqueous coating composition, which may optionally include one or moreorganic solvents. In preferred embodiments, the multi-stage polymericlatex is formulated in combination with a water-dispersible polymer.Typically, the multi-stage polymeric latex is formed in the presence ofthe water-dispersible polymer. While not intending to be bound bytheory, it is believed the water-dispersible polymer can function as asurfactant to support formation and stability of the multi-stagepolymeric latex.

Epoxy-acrylate copolymers (also referred to as epoxy-acrylic copolymers)with over-polymerized emulsion polymerized acrylics have been used infood or beverage can coatings. The epoxy polymer portion of such systemswas conventionally BPA-based (e.g., polymers formed via reaction ofbisphenol A with a diglycidyl ether of bisphenol A) and the acrylic wasrich in styrene content. It was generally understood by those skilled inthe art that certain end use critical coating performance attributes(e.g., sufficient flexibility for a food or beverage can coating enduse) of such conventional epoxy-acrylic systems derived primarily, oreven exclusively, from the epoxy polymer, with the acrylic contentfunctioning primarily as inexpensive filler to allow the amount of moreexpensive epoxy polymer to be minimized. Because the acrylic content insuch conventional systems was believed to contribute little to coatingperformance properties, it was understood by those skilled in the artthat the amount of epoxy polymer in such epoxy-acrylic systems shouldgenerally be more than about 50% by weight of the overall resin systemto avoid unsuitable degradation in coating properties.

The system of the present invention has surprisingly allowed the amountof epoxy polymer employed to be dramatically reduced relative to suchconventional systems while still achieving a comparable balance ofcoating properties, including without the use of either BPA or styrenein some embodiments. For example, in the Examples section below, a latexresin system is exemplified that exhibits a suitable balance of coatingproperties with 80% by weight of total “acrylic” polymer content andonly 20% by weight of polyether polymer content (which can also bereferred to as an “epoxy” polymer, e.g., due to the reactants used tomake it). Surprisingly, such results were achieved without the use ofeither BPA or styrene, which are generally acknowledged by those skilledin the art as bringing beneficial coating properties that are difficultto replicate with alternate materials.

In the preceding paragraph, the term “acrylic” in the context of“acrylic polymer content” is intended to be construed broadly toindicate the amount of polymerized (emulsion polymerized or otherwisepolymerized) ethylenically unsaturated monomer present. Suchethylenically unsaturated monomers are typically vinyl monomers—some orall of which are typically either (meth)acrylic acids or(meth)acrylates. A preponderance (e.g., >50 wt. %, >60 wt. %, >70 wt.%, >80 wt. %, >90 wt. %, etc.), and in some embodiments all orsubstantially all, of the acrylic polymer content of the coatingcomposition comprises emulsion polymerized ethylenically unsaturatedmonomers (e.g., the lower Tg and higher Tg emulsion polymerized stages).In some embodiments (e.g., in which the water-dispersible polymer is apolyether-acrylate, polyester-acrylate, etc.), the acrylic polymercontent also includes organic solution polymerized ethylenicallyunsaturated monomers, which typically include one or more (meth)acrylicacids or (meth)acrylates. In preferred embodiments, acrylic polymercontent constitutes more than 50 wt. %, preferably at least 60 wt. %,even more preferably at least 65 wt. %, even more preferably at least 70wt. %, even more preferably at least 75 wt. %, and optimally 80 wt. % ormore of the resin system, based on the combined weight of thewater-dispersible polymer and the monomers used to form the emulsionpolymerized stages. In some embodiments, the resin system constitutes 70to 100 wt. % of the total resin solids in the coating composition.

While not intending to be bound by theory, it is believed the suitablebalance of coating properties exhibited by preferred embodiments of thelatex resin system of the present invention, including excellentflexibility, can be achieved, even when using very low amounts ofpolyether polymer or other water-dispersible polymer, due to the latexresin system's novel multi-stage structure. In particular, a multi-stagelatex resin system is preferably employed that includes two or moredifferent emulsion polymerized stages having sufficiently different Tgvalues to achieve the desired balance of coating properties. Such Tgdifferences may be achieved via multiple approaches, some of which aredescribed below.

Usually a multi-stage latex will not exhibit a single Tg inflectionpoint as measured via differential scanning calorimetry (“DSC”). Forexample, a DSC curve for a multi-stage latex made using discrete chargesof two or more monomers may exhibit two or more Tg inflection points.Also, a DSC curve for a multi-stage latex made using acontinuously-varied charge of two or more monomers may exhibit no Tginflection points. By way of further explanation, a DSC curve for asingle stage latex made using a single monomer charge or a non-varyingcharge of two monomers may exhibit only a single Tg inflection point.Occasionally when only one Tg inflection point is observed it may bedifficult to determine whether the latex represents a multi-stage latex.In such cases a further (e.g., lower or higher) Tg inflection point maysometimes be detected on closer inspection, or the synthetic scheme usedto make the latex may be examined to determine whether or not amulti-stage latex would be expected to be produced. When evaluating suchTg inflection points, it may be necessary to exclude inflection pointsof non-latex polymers that may also be present in a latex polymercomposition.

In some embodiments, the multi-stage latex polymer is formed fromingredients including a “lower” Tg ethylenically unsaturated monomercomponent and a “higher” Tg ethylenically unsaturated monomer component.The lower Tg and higher Tg monomer components can be emulsionpolymerized at any time relative to one another. In some embodiments,the lower Tg or the higher Tg monomer component is polymerized in afirst stage and the other monomer component is emulsion polymerized in alater second stage after emulsion polymerization of the first stage hasbeen completed. In other embodiments, emulsion polymerization of thesecond stage may be initiated prior to completion of emulsionpolymerization of the first stage. One or more additional ethylenicallyunsaturated monomer components of any suitable Tg may also optionally beemployed and may be emulsion polymerized before, after, between, orduring polymerization of the lower or high Tg monomer components. Thus,in some embodiments, the multi-stage latex polymer may include three ormore emulsion polymerized stages. However, in some embodiments theemulsion polymerized portions of the multi-stage latex polymer consistsessentially of stages (typically two stages) formed from the higher Tgethylenically unsaturated monomer component and the lower Tgethylenically unsaturated monomer component, respectively.

The lower Tg emulsion polymerized stage preferably has a calculated Tgthat is at least 20° C. lower, at least 30° C. lower, at least 35° C.lower, at least 40° C. lower, at least 50° C. lower, at least 60° C.lower, or at least 70° C. lower than a calculated Tg of the higher Tgemulsion polymerized stage. For sake of convenience, in the discussionthat follows the term “stage(s)” is used in place of “emulsionpolymerized stage(s).” Preferably, more than 50 weight percent of thestages present in the multi-stage latex have a calculated Tg of at least40° C., at least 50° C., at least 60° C., at least 70° C., or at least80° C.

Typically, the higher Tg stage will have a calculated Tg of greater than40° C., greater than 45° C., greater than 50° C., greater than 60° C.,greater than 70° C., or greater than 80° C. Although the Tg of thehigher Tg stage is not particularly restricted, typically it will beabout 105° C. or less. The lower Tg stage will typically have acalculated Tg of less than 40° C., more typically less than 35° C., andeven more typically less than 30° C. In some embodiments the lower Tgstage has a calculated Tg of less than 20° C., less than 10° C., lessthan 0° C., or even −10° C. or less. The lower Tg stage will typicallyhave a calculated Tg of about −54° C. or greater.

In certain preferred embodiments, the higher Tg stage has a calculatedTg of greater than 40° C., the lower Tg stage has a calculated Tg ofless than 40° C., and the higher Tg stage Tg value is at least 20° C.greater than that of the lower Tg stage. In some embodiments, the higherTg stage has a calculated Tg of greater than 45° C., the lower Tg stagehas a calculated Tg of less than 35° C. and the higher Tg stage Tg valueis at least 20° C. greater than that of the lower Tg stage. In someembodiments, the higher Tg stage has a calculated Tg of greater than 50°C. and the lower Tg stage has a calculated Tg of less than 30° C. Insome embodiments, the higher Tg stage has a calculated Tg of greaterthan 60° C. and the lower Tg stage has a calculated Tg of less than 20°C. In some embodiments, the higher Tg stage has a calculated Tg ofgreater than 70° C. and the lower Tg stage has a calculated Tg of lessthan 10° C.

The Tg of a particular stage, or combination of stages, can be estimated(viz., calculated) using the Fox equation. For example, for a polymermade from two monomer feeds, the theoretical Tg may be calculated usingthe Fox equation as follows:1/Tg=W _(a) /T _(ga) +W _(b) /T _(gb)

-   -   where T_(ga) and T_(gb) are the respective glass transition        temperatures of homopolymers made from monomers “a” and “b”; and        -   W_(a) and W_(b) are the respective weight fractions of            polymers “a” and “b”.            When additional monomer feeds “c”, “d” and so on are            employed, additional fractions W_(c)/T_(gc), W_(d)/T_(gd)            and so on are added to the right-hand side of the above            equation. Unless indicated otherwise, the “calculated” stage            or copolymer Tg's referenced herein are calculated using the            Fox equation. Also, the calculation is based on all of the            monomers that are reacted together to form a stage, and not            upon merely a portion of such monomers. If an emulsion            polymerized ethylenically unsaturated monomer component            (e.g., a monomer mixture used to form the higher Tg stage or            the lower Tg stage) includes more than 5% by weight of one            or more monomers not having a homopolymer Tg (e.g., because            the monomer cannot be homopolymerized), then instead of            relying on the Fox equation, a single-stage reference latex            can be made using the same overall monomer composition as            the emulsion polymerized ethylenically unsaturated monomer            component and the actual Tg measured via DSC. If the            emulsion polymerized ethylenically unsaturated component            includes 5% by weight or less of one or more monomers not            having a homopolymer Tg, then the one or more such monomers            can be ignored and the Tg determined by the Fox equation.

In some embodiments, a gradient Tg approach may be used to polymerizethe multi-stage latex polymer, or a portion of the multi-stage latexpolymer. When a gradient Tg approach is used, it should be noted that itmay not be possible to measure a discrete Tg for certain latex polymers,and certain gradient Tg latex polymers may contain an almost infinitenumber of Tg stages. For example, one may start with a higher Tg monomercomposition and then at a certain point in the polymerization start tofeed a lower Tg stage monomer composition into the higher Tg stagemonomer feed (or vice versa). The resulting multi-stage latex polymerwill have a gradient Tg from high to low (or vice versa). A “power feed”process may be used to prepare such compositions. A gradient Tg polymermay also be used in conjunction with multiple multi-stage Tg polymers.As an example, one may prepare a higher Tg monomer feed (F1) and a lowerTg monomer feed (F2). One would begin to feed F1 into the latex reactorvessel and initiate polymerization of a higher Tg “hard stage” monomercomposition. At a certain period during the F1 feed, one would then feedF2 into F1 wherein the F2 feed rate is faster than the overall feed rateof F1+F2 into the reactor vessel. Consequently, once the F2 feed into F1is complete, the overall Tg of the F1+F2 monomer feed blend will be alower Tg “soft stage” monomer composition. When a gradient Tg approachis employed, a composite Tg may be calculated by using the Fox equationfor all the monomers and their respective fractions in the finalcopolymer, without regard to which stage or stages may contain suchmonomers. In some embodiments, the composite Tg is at least 0° C., atleast 20° C., at least 30° C., at least 40° C., or at least 50° C. Ifthe monomers used to produce such gradient Tg latex polymers include oneor more monomers not having a homopolymer Tg (e.g., because the monomerdoes not homopolymerize), then a non-gradient reference latex can bemade, in a non-power feed method, using the same overall monomercomposition and used to measure Tg.

For gradient Tg latex polymers, a Tg differential may be determined byusing the Fox equation to calculate the theoretical Tg for a copolymermade from the monomer feed at the start of polymerization and comparingthe result to the calculated theoretical Tg for a copolymer made fromthe monomer feed at the end of polymerization. For multi-stage polymersmade using such a gradient Tg approach, the Tg differential in thecalculated Tg of monomers fed at the start of polymerization compared tomonomers fed at the end of polymerization of the gradient-fed monomerspreferably is at least 20° C., at least 30° C., at least 35° C., atleast 40° C., at least 50° C., at least 60° C., or at least 70° C.

Any suitable weight ratio of lower Tg stage(s) to higher Tg stage(s) maybe employed. In some embodiments, a slight to substantial majority ofhigher Tg stage(s) relative to lower Tg stages(s) is employed.Typically, the weight ratio of the lower Tg stage relative to the higherTg stage (viz., lower Tg stage: higher Tg stage) will be from 5:95 to95:5, more typically from 20:80 to 70:30, and even more typically from25:75 to 48:52. The above weight ratios are based on the weights of theethylenically unsaturated components (typically monomers) used toproduce the respective stages. In certain preferred embodiments, thehigher Tg stage constitutes more than 50 weight percent of the totalemulsion polymerized stages (viz., the combined weight of the lower Tgstage, the higher Tg stage, and any additional stages that mayoptionally be present). While not intending to be bound by theory,interior can coatings that will be exposed to sensitive flavor products(e.g., certain colas in which certain flavorants are present at very lowconcentrations) or chemically aggressive food or beverage products(e.g., high acid, high salt, or high fat) can benefit from the inclusionof a sufficient amount of suitable higher Tg components (e.g., thehigher Tg stage). The challenge in such situations, however, is topreserve the overall balance of coating properties, including forexample, coating flexibility. Again, while not intending to be bound bytheory, it is believed the inclusion of a sufficient amount of suitablelower Tg components (e.g., the lower Tg stage) can help avoid unsuitabledegradation in other desired coating properties such as, e.g.,flexibility.

Any suitable ethylenically unsaturated monomer or combinations ofmonomers can be used to form each of the stages of the multi-stage latexpolymer. Typically, a mixture of two or more monomers is used to formeach stage. In preferred embodiments, the coating compositions include,based on total resin solids, at least 50 wt. %, at least 60 wt. %, atleast 70 wt. %, at least 75 wt. %, or at least 80 wt. % of the two ormore emulsion polymerized stages. In some such embodiments, the coatingcompositions include such an amount of high Tg and low Tg stages, basedon the total amount of reactants used to form the high Tg and low Tgstages relative to the total resin solids.

As discussed herein, the resin system may also optionally includepolymerized ethylenically unsaturated monomers that are polymerizedusing polymerization techniques other than emulsion polymerization(e.g., free radical organic solution polymerization). In preferredembodiments, the total amount of polymerized ethylenically unsaturatedmonomers constitutes more than 50 wt. %, preferably more than 60 wt. %,even more preferably more than 70 wt. %, and optimally 80 wt. % or moreof the total resin solids of the coating composition.

In some embodiments, the emulsion polymerized monomers of the higher Tgand lower Tg stages comprise at least 50 wt. %, at least 60 wt. %, atleast 75 wt. %, or at least 85 wt. % or more of the total amount ofpolymerized ethylenically unsaturated monomers present in the coatingcomposition.

The coating composition of the present invention is preferablyformulated using a resin system that includes a water-dispersiblepolymer and two or more emulsion polymerized stages. Thewater-dispersible polymer may be incorporated into the multi-stagepolymeric latex, blended with the multi-stage polymeric latex, or both.In presently preferred embodiments, the two or more emulsion polymerizedstages are formed by emulsion polymerizing the monomers used to makesuch stages in the presence of the water-dispersible polymer.

While it is contemplated that one or more ethylenically unsaturatedmonomer components may be polymerized separate from thewater-dispersible polymer, in preferred embodiments, the ethylenicallyunsaturated monomer components used to make the two or more emulsionpolymerized stages are polymerized in an aqueous composition thatincludes the water-dispersible polymer dispersed therein. Preferably,the water-dispersible polymer functions as a “polymeric surfactant” thathelps support emulsion polymerization of two or more stages containingthe ethylenically unsaturated monomer components. By way of example, apolymer that is only stably dispersible in an aqueous medium with theassistance of a conventional external surfactant is not considered to bewater-dispersible. By way of further example, a stage (e.g., firststage) of a latex polymer that is polymerizable only with the assistanceof such an external surfactant is not itself considered to be awater-dispersible polymer herein. In some embodiments, the multi-stagelatex is emulsion polymerized in the presence of the water-dispersiblepolymer without the use of conventional non-polymeric surfactants (e.g.,without the use of a low molecular weight surfactant such as sodiumlauryl sulfate (288.4 g/mol), sodium dodecylbenzene sulfonate (348.5g/mol), dioctyl sulfosuccinate sodium salt (444.5 g/mol),amine-neutralized dodecyl benzene sulfonic acid (326.5 g/mol notcounting the amine molecular weight), e.g., ethoxylated fatty alcoholether sulfate sodium salt (1.022 g/mol plus the ethylene oxide weight)or other such conventional surfactants). Thus in some embodiments, theemulsion polymerized ethylenically unsaturated monomer component, andoften the entire resin system, does not include and is not derived fromlow molecular weight non-polymeric surfactants, e.g., low molecularweight anionic, cationic or nonionic surfactants. If any suchsurfactants are employed, their total amount preferably is no more than0.5 wt. %, more preferably no more than 0.25 wt. % and most preferablyno more than 0.1 wt. % of the aggregate weight of the polymerizablemonomers employed to make the latex, and excluding the weight of anymonomers employed to make a seed polymer prior to or at the start ofpolymerization of the latex. Such surfactants are also preferablyamine-functional surfactants or amine-neutralized surfactants, as theamine tends to be volatilized from the coating under bake cureconditions.

In some embodiments, the multi-stage latex is also or instead emulsionpolymerized in the presence of one or more polymerizable surfactants.Examples of suitable polymerizable surfactants include those disclosedin U.S. Patent Application Publication No. 2002/0155235; PublishedInternational Application No. WO 2016/105504A1; and those commerciallyavailable under the tradename “REASOAP” from Adeka Corporation, Tokyo,Japan., under the tradenames “NOIGEN” and “HITENOL” from Da-Ichi KogyoSiyyaku Co., Ltd., Tokyo, Japan; and under the tradename “SIPOMER” fromSolvay Rhodia, Brussels, Belgium. In embodiments that includepolymerizable surfactants, the polymerizable surfactants may constitutegreater than about 0.1%, greater than about 1%, greater than about 2%,or greater than about 3% by weight, based on the total weight of thereactant monomers. The polymerizable surfactant may also constitute lessthan about 25%, less than about 20%, less than about 15%, or less thanabout 10% by weight, based on the aggregate weight of the polymerizablemonomers employed to make the latex, and excluding the weight of anymonomers employed to make a seed polymer prior to or at the start ofpolymerization of the latex.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component is derived using primarily or only low molecularweight surfactants, e.g., low molecular weight anionic or nonionicsurfactants. The concentration of such low molecular weight surfactantsmay vary depending on the types and concentrations of the reactantcomponents, including the presence of any other polymerizable orpolymeric surfactants. In embodiments that include low molecular weightsurfactants, the low molecular weight surfactants may constitute greaterthan about 0.01%, greater than about 0.05%, or greater than about 0.1%by weight, based on the aggregate weight of the polymerizable monomersemployed to make the latex, and excluding the weight of any monomersemployed to make a seed polymer prior to or at the start ofpolymerization of the latex. The low molecular weight surfactants mayalso constitute less than about 10%, less than about 7%, or less thanabout 5% by weight, based on the aggregate weight of the polymerizablemonomers employed to make the latex, and excluding the weight of anymonomers employed to make a seed polymer prior to or at the start ofpolymerization of the latex.

Any suitable amount of the water-dispersible polymer may be used. Inpreferred embodiments, the weight ratio of water-dispersible polymer toemulsion polymerized stages is less than 50:50; preferably less than40:60; and even more preferably less than 30:70, less than 25:75, orless than 20:80.

The water-dispersible polymer can be any suitable polymer or combinationof polymers including, for example, one or more acrylic polymers,polyester polymers, polyether polymers, polyolefin polymers,polysilicone polymers, polyurethane polymers, or copolymers thereof(e.g., polyether-acrylate copolymers, polyester-acrylate copolymers,etc.). Typically, the water-dispersible polymer is not formed in aqueousmedia, and instead may for example be formed in solvent media or in asolventless process and then made dispersible into aqueous media, e.g.,by neutralization of one or more groups on the polymer to convert suchgroups into water-dispersing groups. The water-dispersible polymer mayhave any suitable water-dispersing group or groups. As used herein, theterm “water-dispersing groups” also encompasses water-solubilizinggroups. Typically, the water-dispersible polymer will include one ormore polar groups, more typically one or more salt groups (e.g., anionicsalt groups such as base-neutralized acid or anhydride groups orcationic salt groups such as acid-neutralized base groups) orsalt-forming groups (e.g., base groups or acid or anhydride groups). Inpreferred embodiments, the water-dispersible polymer is an acid- oranhydride-functional polymer in which preferably a suitable amount ofthe acid or anhydride groups have been neutralized with a suitable base,more preferably a fugitive base (e.g., nitrogen-containing bases such asammonia or amines).

The water-dispersible polymer may have any suitable acid number so longas the polymer is preferably capable of being stably dispersed intowater. Preferred acid- or anhydride-functional water-dispersiblepolymers have an acid number of at least about 40, more preferably atleast about 55, and even more preferably at least about 70 milligrams(mg) KOH per gram of the polymer. While the upper range of suitable acidnumbers is not particularly restricted, typically the acid number willbe less than about 400, more typically less than about 300, and evenmore typically less than about 200 mg KOH per gram of the polymer. Acidnumbers referred to herein may be calculated pursuant to BS EN ISO3682-1998 standard, or alternatively may be theoretically determinedbased on the reactant monomers.

Examples of neutralized acid groups include carboxylic acid or anhydridegroups that have been at least partially neutralized with a suitablebase. Fugitive bases are presently preferred, with nitrogen-containingbases being preferred, and amines (e.g., primary, secondary, or tertiaryamines) being particularly preferred. In certain embodiments, the amineis a tertiary amine. Preferably, the tertiary amine is selected fromtrimethyl amine, dimethylethanol amine (also known as dimethylaminoethanol), methyldiethanol amine, triethanol amine, ethyl methyl ethanolamine, dimethyl ethyl amine, dimethyl propyl amine, dimethyl3-hydroxy-1-propyl amine, dimethylbenzyl amine, dimethyl2-hydroxy-1-propyl amine, diethyl methyl amine, dimethyl1-hydroxy-2-propyl amine, triethyl amine, tributyl amine, N-methylmorpholine, and mixtures thereof. In certain preferred embodiments, anacid- or anhydride-functional polymer is at least 25% neutralized withthe amine in water.

In some embodiments, the water-dispersible polymer includes afree-radical polymerized ethylenically unsaturated monomer component(e.g., a styrene-containing or styrene-free vinyl addition component).In preferred such embodiments, the vinyl addition component is formedfrom an ethylenically unsaturated monomer mixture that includes one ormore acid- or anhydride-functional monomers (e.g., methacrylic acid) andtypically one or more (meth)acrylates, more typically one or moremethacrylates, and even more typically one or more alkyl methacrylates(e.g., ethyl methacrylate or butyl methacrylate), optionally incombination with one or more acrylates or alkyl acrylates (e.g., ethylacrylate), wherein the monomer mixture is polymerized in organic solventin the presence or absence of the water-dispersible polymer.

In some embodiments, the water-dispersible polymer is apolyether-acrylate copolymer (alternatively referred to as a“polyether-acrylic” copolymer), more preferably an aromaticpolyether-acrylate that optionally does not contain any structural unitsderived from styrene. In such embodiments, a polyether polymer used toform the polyether-acrylate copolymer preferably comprises at least 30wt. %, more preferably at least 50 wt. %, and even more preferably atleast 60 wt. % or more of the polyether-acrylate copolymer, based on thetotal weight of the polyether-acrylate copolymer. Typically, thepolyether polymer will constitute less than 95 wt. %, more typicallyless than 90 wt. %, and even more typically less than 85 wt. % of thepolyether-acrylate copolymer.

In some embodiments, the water-dispersible polymer may be a phosphatedpolymer. Examples of such water-dispersible polymers include reactionproducts of polymers having oxirane groups, preferably aromaticpolyether polymers having oxirane groups, and phosphoric acid or relatedcompounds. A specific example of such a water-dispersible polymer is anaromatic polyether phosphate ester polymer. Such phosphated polymers mayadditionally include one or more other salt groups to enable desiredmolecular weight and water-dispersibility properties to be achieved.

The water-dispersible polymer can have any suitable molecular weight.Typically, the number average molecular weight (Mn) of thewater-dispersible polymer will be at least 1,500, at least 2,000, atleast 3,000, or at least 4,000, as determined using gel permeationchromatography (“GPC”) and a polystyrene standard. Typically, thewater-dispersible polymer will have an Mn of less than 50,000, less than20,000, less than 10,000, or less than 8,000.

In some embodiments, the polyether polymer has a calculated Tg of atleast 30° C., more preferably at least 60° C., and even more preferablyat least 70° C. or at least 80° C. Typically, the Tg of the polyetherpolymer will be less than 150° C., more typically less than 130° C., andeven more typically less than 110° C. In this context, the Tg refer tothe Tg value of the polyether polymer alone (e.g., prior to forming apolyether-acrylate copolymer). In embodiments in which thewater-dispersible polymer is a polyether polymer or polyether-acrylatecopolymer formed from ingredients including a polyether polymer, thepolyether polymer will typically have a number average molecular weight(Mn) of at least 2,000, more typically at least 3,000, and even moretypically at least 4,000. The molecular weight of the polyether polymermay be as high as is needed for the desired application. Typically,however, the Mn of the polyether polymer will not exceed about 11,000.In some embodiments, the polyether polymer has an Mn of about 5,000 toabout 8,000. In embodiments where the water-dispersible polymer is apolyether-acrylate copolymer, the molecular weight of the overallpolymer may be higher than that recited above, although the molecularweight of the polyether polymer portion will typically be as describedabove. Typically, however, such polyether-acrylate copolymers will havean Mn of less than about 20,000.

A variety of acid- or anhydride-functional monomers, or salts thereof,can be incorporated into the water-dispersible polymer; their selectionis dependent on the desired final polymer properties. In someembodiments, such monomers are ethylenically unsaturated, morepreferably, alpha, beta-ethylenically unsaturated. Suitableethylenically unsaturated acid- or anhydride-functional monomers for thepresent invention include monomers having a reactive carbon-carbondouble bond and an acidic or anhydride group, or salts thereof.Preferred such monomers have from 3 to 20 carbons, at least 1 site ofunsaturation, and at least 1 acid or anhydride group, or salt thereof.

Suitable acid-functional monomers include ethylenically unsaturatedacids (e.g., mono-protic or diprotic), anhydrides or monoesters of adibasic acid, which are copolymerizable with the optional othermonomer(s) used to prepare the polymer. Illustrative monobasic acids arethose represented by the structure CH₂═C(R⁵)—COOH, where R⁵ is hydrogenor an alkyl group of 1 to 6 carbon atoms. Suitable dibasic acids includethose represented by the formulas R⁶(COOH)C═C(COOH)R⁷ andR⁶(R⁶)C═C(COOH)R⁸COOH, where R⁶ and R⁷ are each independently hydrogen,an alkyl group of 1 to 8 carbon atoms, a halogen, a cycloalkyl group of3 to 7 carbon atoms or a phenyl group, and R⁸ is an alkylene group of 1to 6 carbon atoms. Half-esters of these acids with alkanols of 1 to 8carbon atoms are also suitable.

Examples of useful ethylenically unsaturated acid-functional monomersinclude acids such as, for example, acrylic acid, methacrylic acid,alpha-chloroacrylic acid, alpha-cyanoacrylic acid, crotonic acid,alpha-phenylacrylic acid, beta-acryloxypropionic acid, fumaric acid,maleic acid, sorbic acid, alpha-chlorosorbic acid, angelic acid,cinnamic acid, p-chlorocinnamic acid, beta-stearylacrylic acid,citraconic acid, mesaconic acid, glutaconic acid, aconitic acid,tricarboxyethylene, 2-methyl maleic acid, itaconic acid, 2-methylitaconic acid, methyleneglutaric acid, and the like, or mixturesthereof. Preferred unsaturated acid-functional monomers include acrylicacid, methacrylic acid, crotonic acid, fumaric acid, maleic acid,2-methyl maleic acid, itaconic acid, 2-methyl itaconic acid, andmixtures thereof. More preferred unsaturated acid-functional monomersinclude acrylic acid, methacrylic acid, crotonic acid, fumaric acid,maleic acid, itaconic acid, and mixtures thereof. Most preferredunsaturated acid-functional monomers include acrylic acid, methacrylicacid, maleic acid, crotonic acid, and mixtures thereof. Examples ofsuitable ethylenically unsaturated anhydride monomers include compoundsderived from the above acids (e.g., as pure anhydride or mixtures ofsuch). Preferred anhydrides include acrylic anhydride, methacrylicanhydride, and maleic anhydride. If desired, aqueous salts of the aboveacids may also be employed.

Polyether polymers are preferred water-dispersible polymers, witharomatic polyethers or polyethers rich in other cyclic groups beingpreferred, which are preferably substantially free of or do not containeach of BPA, BPF, and BPS, including epoxides thereof, beingparticularly preferred. Such polyether polymers typically includesecondary hydroxyl groups, more typically secondary hydroxyl groupspresent in backbone —CH₂CH(OH)CH₂— segments. In preferred embodiments,the polyether polymer is derived from ingredients including (i) analiphatic, cycloaliphatic, or aromatic diepoxide and (ii) an extendercompound capable of building the molecular weight of the diepoxide toform a polymer. The above (i) and (ii) may be reacted together in anappropriate ratio such as, e.g., about 1.05:1 to about 1:1.05stoichiometric ratio. In some embodiments the diepoxide and the extendercontain similar structural units (e.g., a residue of a diphenol in thediepoxide and the same diphenol in the extender). In other embodimentsthe diepoxide and the extender contain dissimilar structural units(e.g., a residue of a diphenol in the diepoxide and a different diphenolin the extender). In some embodiments the diepoxide, the extender orboth include two ring oxygen atoms with at least one substituent or bond(e.g., a bond to an aryl ring) located ortho to a ring oxygen atom. Inother embodiments the diepoxide, the extender or both include two ringoxygen atoms with substituents or bonds located in both ortho ringpositions relative to the ring oxygen atoms. In further embodiments thediepoxide, the extender or both include two ring oxygen atoms with nosubstituents or bonds located ortho to a ring oxygen atom.

Examples of suitable extender compounds include diols, diacids, andcompounds having both an acid and a hydroxyl group. Polyhydric phenols(e.g., dihydric phenols) are preferred extenders, with polyhydricmonophenols (e.g., dihydric monophenols) being preferred in certainembodiments. Examples of dihydric monophenol compounds include catecholand substituted catechols (e.g., 3-methylcatechol, 4-methylcatechol,4-tert-butyl catechol, and the like); hydroquinone and substitutedhydroquinones (e.g., methylhydroquinone, 2,5-dimethylhydroquinone,trimethylhydroquinone, tetramethylhydroquinone, ethylhydroquinone,2,5-diethylhydroquinone, triethylhydroquinone, tetraethylhydroquinone,tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and the like);resorcinol and substituted resorcinols (e.g., 2-methylresorcinol,4-methyl resorcinol, 2,5-dimethylresorcinol, 4-ethylresorcinol,4-butylresorcinol, 4,6-di-tert-butylresorcinol,2,4,6-tri-tert-butylresorcinol, and the like); and variants and mixturesthereof. Examples of dihydric diphenol compounds include4,4′-methylenebis(2,6-dimethylphenol) (tetramethyl bisphenol F),4,4′-(ethane-1,2-diyl)bis(2,6-dimethylphenol),4,4′-butylidenebis(2-t-butyl-5-methylphenol),4,4′-methylenebis(2,6-di-t-butylphenol),2,2′-methylenebis(4-methyl-6-t-butylphenol,4,4′-(ethane-1,2-diyl)bis(2,6-dimethylphenol), tetrabromobisphenol A,2,2′-biphenol and other bridged dihydric phenols having a ring to ringbridge linkage located ortho to a phenol oxygen atom, and the like.Other suitable dihydric diphenol compounds include those described inU.S. Patent Application Publication No. US 2015/0197597 A1 and PublishedInternational Application No. WO 2018/125895 A1. Although not preferredfor use in all instances, bisphenol compounds such as bisphenol A,bisphenol F and bisphenol S may be employed in some end uses, in somejurisdictions, or in admixture with other extender compounds, forexample to reduce raw material costs.

Examples of suitable diepoxides include diepoxides of (e.g., diglycidylethers or esters of): substituted dihydric phenols (e.g.,ortho-substituted dihydric phenols such as tetramethyl bisphenol F,di-tert-butylhydroquinone, 2,2′-biphenol and other bridged dihydricphenols having a ring to ring bridge linkage located ortho to a phenoloxygen atom, and the like), aromatic diols (e.g., benzene dimethanol,vanillyl alcohol, furan dimethanol, and the like), aromatic diacids(e.g., isophthalic acid, terephthalic acid, and the like), aliphaticdiols, aliphatic diacids, cycloaliphatic diols (e.g., cyclobutane diolssuch as 2,2,4,4-tetramethyl-1,3-cyclobutanediol and cyclohexanedimethanol), cycloaliphatic diacids (e.g., cyclobutane diacids such as2,2,4,4-tetramethyl-1,3-cyclobutane dicarboxylic acid), and combinationsthereof. Other suitable diepoxides include the diglycidyl ethercompounds described in U.S. Patent Application Publication No. US2015/0197597 A1 and Published International Application Nos. WO2017/079437 A1 and WO 2018/125895 A1. Although not preferred for use inall instances, diepoxides (e.g., diglycidyl ethers) of bisphenolcompounds such as bisphenol A, bisphenol F and bisphenol S may beemployed in some end uses, in some jurisdictions, or in admixture withother diepoxides, for example to reduce raw material costs.

In some embodiments, the water-dispersible polymer is a reaction productof ingredients including a dihydric phenol and a diepoxide of a dihydricphenol (e.g., reacted in an appropriate ratio such as, e.g., about1.05:1 to about 1:1.05 stoichiometric ratio).

Examples of suitable polyether polymers include those disclosed in U.S.Pat. No. 9,409,219 B2; in U.S. Patent Application Publication Nos. US2015/0021323 A1, US 2015/0151878 A1, 2015/0197597 A1, US 2016/0272576A1, US 2017/0051177 A1, US 2017/0096521 A1 and US 2017/0096579 A1; andin Published International Application Nos. WO 2017/079437 A1 and WO2018/125895 A1.

In some embodiments (for example, those prepared without the use of awater-dispersible polyether polymer), one or more of the disclosed latexdispersion, resin system and aqueous coating composition does notcontain polyether compounds or polymers. In other embodiments, the totalamount of such polyether compounds or polymers will be less than 10 wt.%, less than 5 wt. % or less than 1 wt. % based on the total solids inthe dispersion, resin system or coating composition.

Polymers that are not reducible in water can be renderedwater-dispersible using technologies well known to those of skill in theart. In some embodiments, the polymer (e.g., aromatic polyether polymeror other polymer) is covalently attached to one or more materials (e.g.,monomers, oligomers or polymers) having one or more water-dispersinggroups (e.g., salt or salt-forming groups) to render the polymerwater-dispersible. The salt, salt-forming, or thewater-dispersible-group-containing material may be, for example,oligomers or polymers that are (i) formed in situ prior to, during, orafter formation of the polymer or (ii) provided as preformed materialsthat are reacted with a preformed, or nascent, polymer. The covalentattachment may be achieved through any suitable means including, forexample, via reactions involving carbon-carbon double bonds, hydrogenabstraction (e.g., via a reaction involving benzoyl peroxide mediatedgrafting via hydrogen abstraction such as, e.g., described in U.S. Pat.No. 4,212,781), or the reaction of complimentary reactive functionalgroups such as occurs, e.g., in condensation reactions. In oneembodiment, a linking compound is utilized to covalently attach thepolymer and a salt- or salt-forming-group-containing material. Incertain preferred embodiments, the one or more materials having salt orsalt-forming groups is a vinyl addition component (e.g., a vinyladdition polymer), which is typically an acrylic material (e.g., isformed from an ethylenically unsaturated monomer component that includesone or more of a (meth)acrylate, a (meth)acrylic acid, and the like),more preferably an acid- or anhydride-functional acrylic material.

In one embodiment, a water-dispersible polymer may be formed frompreformed polymers (e.g., (a) an oxirane-functional polymer, such as,e.g., an oxirane-functional polyether polymer, and (b) anacid-functional polymer such as, e.g., an acid-functional acrylicpolymer) in the presence of an amine, more preferably a tertiary amine.If desired, an acid-functional polymer can be combined with an amine,more preferably a tertiary amine, to at least partially neutralize itprior to reaction with an oxirane-functional polymer.

In another embodiment, a water-dispersible polymer may be formed from anoxirane-functional polymer (more preferably a polyether polymerdescribed herein) that is reacted with ethylenically unsaturatedmonomers to form an acid-functional polymer, which may then beneutralized, for example, with a base such as a tertiary amine. Thus,for example, in one embodiment, a water-dispersible polymer may beformed pursuant to the acrylic polymerization teachings of U.S. Pat. No.4,285,847 or 4,212,781, which describe techniques for graftingacid-functional acrylic groups (e.g., via use of benzoyl peroxide) ontooxirane-functional polymers. In another embodiment, acrylicpolymerization may be achieved through reaction of ethylenicallyunsaturated monomers with unsaturation present in the polymer. See, forexample, U.S. Pat. No. 4,517,322 or U.S. Patent Application PublicationNo. 2005/0196629 for examples of such techniques.

In another embodiment, a water-dispersible polymer may be formed havingthe structure E-L-A, where “E” is a polyether portion of the polymerformed from a polyether polymer, “A” is a polymerized acrylic portion ofthe polymer, and “L” is a linking portion of the polymer whichcovalently links E to A. Such a polymer can be prepared, for example,from (a) a polyether polymer preferably having about two oxirane groups,(b) an unsaturated linking compound preferably having (i) acarbon-carbon double bond, a conjugated carbon-carbon double bond or acarbon-carbon triple bond and (ii) a functional group capable ofreacting with an oxirane group (e.g., a carboxylic group, a hydroxylgroup, an amino group, an amido group, a mercapto group, etc.).Preferred linking compounds include 12 or less carbon atoms, with sorbicacid being an example of a preferred such linking compound. The acrylicportion preferably includes one or more salt groups or salt-forminggroups (e.g., acid groups such as present in α,β-ethylenicallyunsaturated carboxylic acid monomers). Such polymers may be formed, forexample, using a BPA- and BADGE-free polyether polymer as described inthe above-mentioned U.S. Pat. No. 9,409,219 B2, U.S. Patent ApplicationPublication Nos. US 2015/0021323 A1, US 2015/0151878 A1, US 2016/0272576A1, US 2017/0051177 A1, US 2017/0096521 A1 and US 2017/0096579 A1, andPublished International Application No. WO 2018/125895 A1, optionally incombination with the materials and techniques disclosed in U.S. Pat. No.5,830,952 or U.S. Patent Application Publication No. US 2010/0068433 A1.

In the above approaches utilizing an acrylic component to render thepolymer water-dispersible, the acrylic component is typically formedfrom an ethylenically unsaturated monomer mixture that includes one ormore α,β-unsaturated carboxylic acid, although any suitable acid- oranhydride-functional monomer may be used. The one or moreα,β-unsaturated carboxylic acid preferably renders the polymerwater-dispersible after neutralization with a base. Suitableα,β-unsaturated carboxylic acid monomers include any of those previouslyreferenced herein. Although it may be possible to blend the multi-stagelatex polymer and the water-dispersible polymer together, in presentlypreferred embodiments at least some (and in some embodiments all) of theethylenically unsaturated monomer component is emulsion polymerized inan aqueous dispersion including at least some water-dispersible polymer.

Although not wishing to be bound by theory, it may be possible toachieve desirable coating performance for certain end uses within thefood or beverage can coatings area without using any polyether polymer,or for that matter any water-dispersible polymer, in conjunction withthe multi-stage latex of the present invention. Nonetheless, presentlypreferred embodiments include a water-dispersible polymer, withpolyether polymers (e.g., polyether-acrylate copolymers) being preferredwater-dispersible polymers.

Although BPA or styrene may be used, in presently preferred embodiments,the coating composition of the present invention is substantially freeof or does not contain one or more of: (i) styrene and (ii) bisphenol A(“BPA”), bisphenol F (“BPF”), and bisphenol S (“BPS”). By way ofexample, a coating composition that is substantially free of each ofBPA, BPF, and BPS is necessarily also substantially free of each of thediglycidyl ether of BPA (“BADGE), the diglycidyl ether of BPF, and thediglycidyl ether of BPS. In preferred embodiments, the coatingcomposition exhibits a balance of coating properties in food or beveragecan coating end uses that is comparable to conventional epoxy-acrylatecoating systems that utilize substantial amounts of both BPA andstyrene. In some embodiments, the coating composition is alsosubstantially free of or does not contain substituted styrene compounds(e.g., alpha-methylstyrene, methyl styrenes (e.g., 2-methyl styrene,4-methyl styrene, vinyl toluene, and the like), dimethyl styrenes (e.g.,2,4-dimethyl styrene), trans-beta-styrene, divinylbenzene, and thelike). In some embodiments, the coating composition is substantiallyfree of or does not contain vinyl aromatic compounds.

Any combination of one or more (meth)acrylates may be included in thetwo or more emulsion polymerized stages. Suitable (meth)acrylatesinclude any of those referenced herein, as well as those having thestructure of the above-mentioned Formula (II):CH₂═C(R³)—CO—OR⁴  (II)wherein:

-   -   R³ is hydrogen or methyl, and    -   R⁴ is an alkyl group preferably containing one to sixteen carbon        atoms, a cycloaliphatic group, an aryl group, a silane group, or        a combination thereof.

If desired, R⁴ may optionally be substituted with one or more (e.g., oneto three) moieties such as hydroxy, halo, phenyl, and alkoxy, forexample. Examples of suitable (meth)acrylates (including, e.g., suitablealkyl (meth)acrylates) include methyl (meth)acrylate, ethyl(meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl(meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, isoamyl(meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,cyclohexyl (meth)acrylate, decyl (meth)acrylate, isodecyl(meth)acrylate, benzyl (meth)acrylate, phenyl (meth)acrylate, lauryl(meth)acrylate, isobornyl (meth)acrylate, octyl (meth)acrylate, nonyl(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl(meth)acrylate, and the like, substituted variants thereof (e.g., ringsubstituted variants of benzyl (meth)acrylate or phenyl (meth)acrylate),and isomers and mixtures thereof.

In the discussions that follow, various weight percentages are providedpertaining to the constituents of the two or more emulsion polymerizedstages. As will be understood by one of skill in the art, unlessspecifically indicated to the contrary, these weight percentages arebased on the total weight of the reactants (typically monomers) used toform the pertinent stage or stages.

Typically, (meth)acrylates (e.g., one or a mixture of two or more(meth)acrylates) will constitute a substantial portion of each of thetwo or more stages. In some embodiments, (meth)acrylates may constituteat least 30 wt. %, at least 50 wt. %, at least 70 wt. %, at least 85 wt.%, at least 95 wt. %, or even 100 wt. % of the monomers used to form atleast one of the emulsion polymerized stages (and in some embodimentsthe aggregate of monomers used to form the two or more stages). Theaforementioned weight percentages include all (meth)acrylates monomerspresent in the particular stage(s), regardless of whether one or more ofthe monomers may also qualify as a “monomer A” as described below. Insome embodiments, one or more methacrylate monomers are present in anamount recited in this paragraph.

In some embodiments, alkyl (meth)acrylates may constitute at least 30wt. %, at least 50 wt. %, at least 70 wt. %, at least 85 wt. %, at least95 wt. %, or even 100 wt. % of the monomers used to form at least one ofthe emulsion polymerized stages (and in some embodiments the aggregateof monomers used to form the two or more stages). The aforementionedweight percentages include all alkyl (meth)acrylates monomers present,regardless of the fact that all such monomers are also (meth)acrylates,and regardless of whether one or more of the monomers may also qualifyas a “monomer A”.

In some embodiments, the monomers used to form at least one of theemulsion polymerized stages (and in some embodiments the aggregate ofmonomers used to form the two or more emulsion polymerized stages)preferably include at least 50 wt. %, at least 75 wt. %, or at least 80wt. % of one or more (e.g., one, two, three, four, or five) of methylmethacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate (e.g.,n-butyl acrylate), and butyl methacrylate (e.g., n-butyl methacrylate).In some embodiments, the monomers used to form at least one of theemulsion polymerized stages (and in some embodiments the monomers usedto form each of the respective two or more emulsion polymerized stages)include a butyl methacrylate, a butyl acrylate, or both. In someembodiments, the monomers used to form the at least one emulsionpolymerized stage, and in some embodiments the monomers used to formeach of the respective two or more emulsion polymerized stages, include(i) both n-butyl methacrylate and one or both of ethyl methacrylate ormethyl methacrylate and (ii) optionally one or more of ethyl acrylate,methyl acrylate, or n-butyl acrylate.

In some embodiments, a majority (e.g., ≥50 wt. %, ≥60 wt. %, ≥70 wt. %,≥80 wt. %, ≥90 wt. %, ≥95 wt. %, etc.), or even all, of the(meth)acrylates present in the monomers used to form one or more stages(e.g., the higher Tg stage) are methacrylates, more preferably alkylmethacrylates. Examples of preferred methacrylates include methylmethacrylate, ethyl methacrylate, n-propyl methacrylate, n-butylmethacrylate, and isomers thereof (e.g., t-butyl methacrylate, iso-butylmethacrylate, etc.). In addition, di(meth)acrylates andtri(meth)acrylates may be used, with preferred examples includingethanediol dimethacrylate, propanediol dimethacrylate, and butanedioldimethacrylate (e.g., 1,3-butanediol dimethacrylate and 1,4-butanedioldimethacrylate).

Thus, in some embodiments the monomers used to form one or more stages(e.g., the higher Tg stage, and in some embodiments the aggregate ofmonomers used to form the two or more emulsion polymerized stages)include at least 30 wt. %, at least 50 wt. %, at least 70 wt. %, atleast 85 wt. %, or at least 95 wt. % of one or more alkyl methacrylates.

In some embodiments (e.g., certain styrene-free embodiments), themonomers used to form at least one of the emulsion polymerized stagesinclude one or more ethylenically unsaturated monomers that include acycloaliphatic group or a hydrocarbon group including at least fourcarbon atoms (referred to collectively hereinafter as “monomer componentA” or “monomers A” for short), or a mixture of both. Although anysuitable ethylenically unsaturated monomer(s) A may be used, suchmonomers will typically be vinyl monomers such as, for example, alkyl(meth)acrylates, cycloalkyl (meth)acrylates, vinyl aromatics (including,e.g., aryl (meth)acrylates), vinyl esters, and the like. One or moreheteroatoms may optionally be present in the cycloaliphatic group or theC4 or greater hydrocarbon group. In some embodiments, only carbon atomsand hydrogen atoms are present in the cycloaliphatic group or the C4 orgreater hydrocarbon group. The C4 or greater hydrocarbon group can haveany suitable structure, although linear chains or branched linear chainsare preferred in some embodiments, with linear or branched linear groupshaving a longest chain that includes at least 3 carbon atoms beingparticularly preferred in certain embodiments. Alkyl (meth)acrylateshaving the specified groups are examples of preferred such monomers A,although any suitable type or types of ethylenically unsaturatedmonomers having such groups may be used.

While not intending to be bound by any theory, it is believed that theinclusion of one or more ethylenically unsaturated monomers that includea cycloaliphatic group or a hydrocarbon group having at least fourcarbon atoms can, among other things, help impart a suitably high levelof hydrophobicity. It is believed that this may be desirable formultiple reasons such as, e.g., to enhance water resistance or retortresistance and help reduce partitioning (“scalping”) of lowconcentration flavorants present in certain aqueous packaged products(e.g., certain colas) into the coating. Resistance to unsuitable levelsof flavor scalping is generally desired for interior can coatings,especially for interior beverage can coatings that may be used topackage products such as, e.g., certain colas that may containrelatively low flavorant concentrations where significant partitioningof flavorant into the coating may lead to perceivable changes in productflavor.

Examples of suitable C4 or greater hydrocarbon groups for inclusion inmonomers A include hydrocarbon groups having 4 or more, 5 or more, 6 ormore, 7 or more, or 8 or more carbon atoms, with preferred suchhydrocarbon groups being butyl, pentyl, hexyl, and isomers thereof(e.g., n-butyl, sec-butyl, t-butyl. etc.). Some specific examples ofsuch monomers A include: n-butyl (meth)acrylate, isobutyl(meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate,n-pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate,2-ethylhexyl (meth)acrylate, isodecyl methacrylate, 3,5,5-trimethylhexyl(meth)acrylate, derivatives and isomers thereof, and combinationsthereof. In some embodiments, C4 or greater hydrocarbon groups havingbetween 4 and 6 carbon atoms are preferred. While not intending to bebound by any theory, it is believed that the inclusion of an excessiveamount of monomers A having long linear carbon chains (e.g., C7 orgreater, and in certain instances C5 or C6) may result in a latex havingan unsuitably low glass transition temperature for certain internal cancoating applications. Any suitably cycloaliphatic group may be employedin monomers A, including, for example, cycloaliphatic groups having4-membered rings, 5-membered rings, 6-membered rings, or even 7-memberedrings or larger. The cycloaliphatic groups may also be monocyclic orpolycyclic (e.g., bicyclic, tricyclic, tetracyclic, etc.). Any suitablepolycyclic groups may be employed, including, for example, bridgedpolycyclic ring systems (e.g., norbornane groups), fused polycyclic ringsystems, or combinations thereof (e.g., tricyclodecane groups).Typically, the atoms making up the ring(s) will be carbon atoms,although as discussed above, one or more heteroatoms may also be presentin the ring. Examples of monomers A having a cycloaliphatic groupinclude cyclohexyl (meth)acrylate, 4-tert-butylcyclohexyl(meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, isobornyl(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, variants and isomersthereof, and mixtures thereof.

In some embodiments, butyl (meth)acrylates are preferred monomers A. Insome embodiments, the ethylenically unsaturated monomer componentincludes both butyl acrylate and butyl methacrylate. In some suchembodiments, it may be preferable to use an excess amount of butylmethacrylate relative to the amount of butyl acrylate.

As mentioned above, in some embodiments at least one monomer A of thebelow Formula (I) is employed to prepare one or more of the emulsionpolymerized stages:CH₂═C(R¹)—X_(n)—C(CH₃)_(t)(R²)_(3-t)  (I)wherein:

-   -   R¹ is hydrogen or an alkyl group, more typically hydrogen or a        methyl group;    -   n is 0 or 1, more typically 1;    -   X, if present, is a divalent linking group; more typically an        amide, carbonate, ester, ether, urea, or urethane linkage; and        even more typically an ester linkage of either directionality        (viz., —C(O)—O— or —O—C(O)—);    -   t is 0 to 3;    -   each R², if present, is independently an organic group that may        optionally be itself branched, more typically an alkyl group        that may optionally include one or more heteroatoms (e.g., N, O,        P, Si, etc.); and    -   two or more R² may optionally form a cyclic group with one        another.

In some embodiments, t is 1 and the total number of carbon atoms presentin both R² groups is 6, 7, or 8. Examples of such monomers A include theVEOVA 9 (Tg 70° C.), VEOVA 10 (Tg −3° C.), and VEOVA 11 (Tg −40° C.)monomers commercially available from Hexion.

In some embodiments, t is 0, 1, or 2, and least one R² is a branchedorganic group, more typically a branched alkyl group. Thus, for example,in some embodiments, at least one R² is present that includes a tertiaryor quaternary carbon atom. The VEOVA 9 monomer is an example of such abranched monomer.

In some embodiments, at least one of the emulsion polymerized stages(and in some embodiments the aggregate of monomers used to form the twoor more stages) includes at least 30 weight percent (“wt. %”), at least35 wt. %, at least 40 wt. %, at least 45 wt. %, or even 80 wt. % or moreof one or more monomers A. Although the upper amount is not restricted,when used, the one or more monomers A are typically the present in anamount (in a particular stage or the aggregate of monomers used to formthe two or more stages) of 100 wt. %, more typically less than 80 wt. %,even more typically less than 75 wt. %, and even more typically lessthan 65 wt. %.

In some embodiments, the monomers used to form at least one of theemulsion polymerized stages (and in some embodiments the aggregate ofthe monomers used to form the two or more emulsion polymerized stages)include at least 20 wt. %, at least 30 wt. %, at least 35 wt. %, atleast 40 wt. %, or even 80 wt. % or more of one or more ethylenicallyunsaturated monomers having a linear or branched hydrocarbon groupincluding at least 4 carbon atoms and having a longest chain length ofat least 3 carbon atoms.

In some embodiments, the monomers used to form at least one of theemulsion polymerized stages includes one or more ethylenicallyunsaturated monomers having a C1-C3 hydrocarbon group. The methyl groupattached to the alpha-carbon of methacrylic acid is not considered sucha C1-C3 hydrocarbon group. Similarly, the vinylic group of a vinylmonomer is not considered to be present in such a C1-C3 hydrocarbongroup. Preferred such hydrocarbon groups include methyl, ethyl, propyl,and isopropyl groups. Examples of such monomers include alkyl(meth)acrylates in which the alkyl group (e.g., an R⁴ group in the aboveFormula (II)) is a C1-C3 alkyl group such as, e.g., methyl, ethyl,n-propyl, iso-propyl, and mixtures thereof. Preferred such monomershaving a C1-C3 hydrocarbon group include methyl methacrylate, ethylacrylate, ethyl methacrylate, and mixtures thereof. An emulsionpolymerized ethylenically unsaturated monomer component can include anysuitable amount of such monomers, including, for example at least 10 wt.%, at least 20 wt. %, at least 30 wt. %, or at least 40 wt. %.Typically, the one or more ethylenically unsaturated monomers having aC1-C3 hydrocarbon group will constitute less than 70 wt. %, moretypically less than 60 wt. %, and even more typically less than 50 wt.%.

Multi-functional monomers may be used, with multi-ethylenicallyunsaturated monomers being an example of preferred multi-functionalmonomers. Examples of suitable multi-ethylenically unsaturated(meth)acrylates include polyhydric alcohol esters of acrylic acid ormethacrylic acid, such as ethanediol di(meth)acrylate, propanedioldi(meth)acrylate, butanediol di(meth)acrylate (e.g., 1,3-butanedioldi(meth)acrylate and 1,4-butanediol di(meth)acrylate), heptanedioldi(meth)acrylate, hexanediol di(meth)acrylate, trimethylolethanetri(meth)acrylate trimethylolpropane tri(meth)acrylate,trimethylolbutane tri(meth)acrylate, trimethylolheptanetri(meth)acrylate, trimethylolhexane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipropylene glycol di(meth)acrylate,trimethylol hexane tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, isosorbide di(meth)acrylate, allyl (meth)acrylate,glycerol dimethacrylate, and mixtures thereof. Examples ofmulti-ethylenically unsaturated monomers other than (meth)acrylatesinclude diallyl phthalate, divinylbenzene, divinyltoluene,divinylnaphthalene, and mixtures thereof.

In some embodiments, the monomers used to form at least one stage (andin some embodiments the aggregate of monomers used to form the two ormore emulsion polymerized stages) may include a small amount (e.g., lessthan 5 wt. %, less than 2 wt. %, or less than 1 wt. %) of acid- oranhydride-functional ethylenically unsaturated monomer. Examples ofsuitable such acid- or anhydride-functional monomers may include any ofthose disclosed for use in conjunction with the acrylate portion of anyof the polyether-acrylate copolymers disclosed herein.

The ethylenically unsaturated monomer component may also include anyother suitable monomers. For example, suitable other vinyl monomers mayinclude isoprene, diallylphthalate, conjugated butadiene, vinylnaphthalene, acrylonitrile, (meth)acrylamides (e.g., acrylamide,methacrylamide, N-isobutoxymethyl acrylamide, N-butoxymethyl acrylamide,etc.), methacrylonitrile, vinyl acetate, vinyl propionate, vinylbutyrate, vinyl stearate, and the like, and variants and mixturesthereof.

In some embodiments, the emulsion polymerized ethylenically unsaturatedmonomer component does not contain any oxirane-group containing monomer.

In presently preferred embodiments, the emulsion polymerizedethylenically unsaturated monomer component, and more preferably theentire resin system, does not include and is not derived from anyacrylamide-type monomers (e.g., acrylamides or methacrylamides). If anysuch monomers are employed, their total amount preferably is no morethan 0.5 wt. % and more preferably no more than 0.1 wt. % of theaggregate weight of the polymerizable monomers employed to make theresin system.

The emulsion polymerized ethylenically unsaturated monomer component mayoptionally include one or more vinyl aromatic compounds other thanstyrene. Such vinyl aromatic compounds may be substituted styrenecompounds or other types of vinyl aromatic compounds (e.g., any of thearyl-group-containing ethylenically unsaturated monomers describedherein such as benzyl (meth)acrylate, etc.). In some embodiments, themonomers used to form at least one stage (and in some embodiments theaggregate of monomers used to form the two or more emulsion polymerizedstages) include, if any, less than 20 wt. %, less than 10 wt. %, lessthan 5 wt. % or less than 1 wt. % of vinyl aromatic compounds. In someembodiments, the monomers used to form the latex are substantially freeof or do not contain such compounds.

With regard to the conditions of the emulsion polymerization reactionsdescribed herein, the two or more stages (e.g., the higher Tg and lowerTg stages) of the multi-stage latex are preferably polymerized inaqueous medium with a water-soluble free radical initiator in thepresence of one or more water-dispersible polymers described herein.Although not presently preferred, it is also contemplated that some (oreven all) of the emulsion polymerized ethylenically unsaturatedcomponents of the two or more stages can be emulsion polymerizedseparately and then later mixed with the one or more water-dispersiblepolymers.

The temperature of polymerization is typically from 0° C. to 100° C.,preferably from 50° C. to 90° C., more preferably from 70° C. to 90° C.,and even more preferably from 80° C. to 85° C. The pH of the aqueousmedium is usually maintained at a pH of 5 to 12.

The free radical initiator can be selected, for example, from one ormore water-soluble peroxides which are known to act as free radicalinitiators. Examples include hydrogen peroxide and t-butylhydroperoxide. Redox initiator systems well known in the art (e.g.,t-butyl hydroperoxide, erythorbic acid, and ferrous complexes) can alsobe employed. In some embodiments, a mixture of benzoin and hydrogenperoxide is used.

Further examples of polymerization initiators which can be employedinclude polymerization initiators that thermally decompose at thepolymerization temperature to generate free radicals. Examples includeboth water-soluble and water-insoluble species. Further examples of freeradical initiators that can be used include persulfates, such asammonium or alkali metal (potassium, sodium or lithium) persulfate; azocompounds such as 2,2′-azo-bis(isobutyronitrile),2,2′-azo-bis(2,4-dimethylvaleronitrile), and1-t-butyl-azocyanocyclohexane; hydroperoxides such as t-amylhydroperoxide, methyl hydroperoxide, and cumene hydroperoxide; peroxidessuch as benzoyl peroxide, caprylyl peroxide, di-t-butyl peroxide, ethyl3,3′-di(t-butylperoxy) butyrate, ethyl 3,3′-di(t-amylperoxy) butyrate,t-amylperoxy-2-ethyl hexanoate, and t-butylperoxy pivilate; peresterssuch as t-butyl peracetate, t-butyl perphthalate, and t-butylperbenzoate; as well as percarbonates, such asdi(1-cyano-1-methylethyl)peroxy dicarbonate; perphosphates, and thelike; and combinations thereof.

Polymerization initiators can be used alone or as the oxidizingcomponent of a redox system, which also preferably includes a reducingcomponent such as, e.g., ascorbic acid, malic acid, glycolic acid,oxalic acid, lactic acid, thiogycolic acid, or an alkali metal sulfite,more specifically a hydrosulfite, hyposulfite or metabisulfite, such assodium hydrosulfite, potassium hyposulfite and potassium metabisulfite,or sodium formaldehyde sulfoxylate, and combinations thereof. Thereducing component is frequently referred to as an accelerator or acatalyst activator.

The initiator and accelerator (if any) are preferably used in proportionfrom about 0.001% to 5% each, based on the weight of monomers to becopolymerized. Promoters such as chloride and sulfate salts of cobalt,iron, nickel or copper can be used in small amounts, if desired.Examples of redox catalyst systems include tert-butylhydroperoxide/sodium formaldehyde sulfoxylate/Fe(II), and ammoniumpersulfate/sodium bisulfite/sodium hydrosulfite/Fe(II).

Chain transfer agents can be used to control polymer molecular weight,if desired. Exemplary chain transfer agents include mercaptans and othermaterials that will be familiar to persons having ordinary skill in theart.

The polymerization reaction of ethylenically unsaturated monomers in thepresence of the aqueous dispersion of the water-dispersible polymer maybe conducted as a batch, intermittent, or continuous operation.

Typically, the reactor is charged with an appropriate amount of waterand water-dispersible polymer. Typically, the reactor is then heated tothe free radical initiation temperature and then charged withethylenically unsaturated monomers of a first stage (e.g., of the higherTg stage or the lower Tg stage). There may also be some water misciblesolvent present. At temperature, the free radical initiator is added andis allowed to react for a period of time at polymerization temperature,the remaining ethylenically unsaturated monomer component (if any of afirst stage) is added incrementally with the rate of addition beingvaried depending on the polymerization temperature, the particularinitiator being employed, and the type and amount of monomers beingpolymerized. After, or prior to, completion of the first stagepolymerization, the ethylenically unsaturated monomers of a second stage(e.g., the other of the higher or lower Tg stage) are charged to thereactor, typically along with additional free radical initiator. Afterall the monomers have been charged, a final heating is carried out tocomplete the polymerization. The reactor is then cooled and the latexrecovered. As previously discussed, the method may also include theemulsion polymerization of one or more additional optional stages (e.g.,in addition to the higher Tg and lower Tg stages) at any suitable time.It should be understood that the above methodology is onlyrepresentative and other suitable processes may also be used.

If desired, a non-polymeric surfactant (or emulsifier) may be employedto facilitate emulsion polymerization of one or more of the stages ofthe latex. Such surfactants may optionally be polymerizable and may beused instead of, or in addition to, the water-dispersible polymer.Examples of suitable such non-polymer surfactants are provided, forexample, in Published International Application Nos. WO 2016/105504 A1and WO 2017/112837 A1.

As previously discussed, in preferred embodiments, the water-dispersiblepolymer and two or more emulsion polymerized stages are both present ina latex (e.g., both present in a same latex particle or latexcopolymer), which is preferably formed by emulsion polymerizing the twoor more stages in the presence of the water-dispersible polymer. Thewater-dispersible polymer and one or more of the emulsion polymerizedstages may optionally be covalently attached to one another. Similarly,two or more emulsion polymerized stages (e.g., the higher Tg and lowerTg stages) may be covalently attached to one another.

Coating compositions of the present invention preferably include atleast a film-forming amount of the resin system described hereincontaining the water-dispersible polymer and the two or more emulsionpolymerized stages. The coating composition typically includes at least10 wt. %; more typically at least 20 wt. %; even more typically at least50 wt. %; and even more typically at least 75 wt. %, at least 90 wt. %,or at least 95 wt. % of the resin system; based on the solids weight ofthe water-dispersible polymer and the two or more emulsion polymerizedstages relative to the total resin solids weight of the coatingcomposition. The coating composition includes 100 wt. % or less, moretypically less than 99 wt. %, and even more typically less than 95 wt. %of the resin system (which is preferably a latex resin system), based onthe solids weight of the water-dispersible polymer and the two or moreemulsion polymerized stages relative to the total resin solids weight ofthe coating composition.

Typically, resin solids will constitute at least 30 wt. %, at least 40wt. %, or at least 50 wt. % or more of the coating solids. In someembodiments, resin solids constitute all or substantially all (e.g.,greater than 90 or 95 wt. % or even 100 wt. %) of the coating solids.

The coating composition may be formulated from the latex emulsion,optionally with the inclusion of one or more additives or by rheologicalmodification for different coating applications (e.g., diluted for spraycoating applications). In embodiments in which the coating compositionincludes one or more additives, the additives preferably do notadversely affect the latex emulsion, or a cured coating formed from thecoating composition. For example, such optional additives may beincluded in the coating composition to enhance composition aesthetics,to facilitate manufacturing, processing, handling, and application ofthe composition, and to further improve a particular functional propertyof the coating composition or a cured coating resulting therefrom.

Such optional additives include, for example, catalysts, dyes, pigments,toners, extenders, fillers, lubricants, anticorrosion agents,flow-control agents, thixotropic agents, dispersing agents,antioxidants, adhesion promoters, light stabilizers, curing agents,co-resins and mixtures thereof. Each optional additive is preferablyincluded in a sufficient amount to serve its intended purpose, but notin such an amount to adversely affect the coating composition or a curedcoating resulting therefrom.

One preferred optional additive is a catalyst to increase the rate ofcure. Examples of catalysts, include, but are not limited to, strongacids (e.g., dodecylbenzene sulphonic acid (DDBSA, available as CYCAT600 from Cytec), methane sulfonic acid (MSA), p-toluene sulfonic acid(pTSA), dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, and tin, titanium,and zinc compounds. Specific examples include, but are not limited to, atetraalkyl ammonium halide, a tetraalkyl or tetraaryl phosphonium iodideor acetate, tin octoate, zinc octoate, triphenylphosphine, and similarcatalysts known to persons skilled in the art.

If used, the catalyst is preferably present in an amount of at leastabout 0.01% by weight, and more preferably at least about 0.1% byweight, based on the total solids weight of the coating composition.Furthermore, if used, the catalyst is also preferably present in annon-volatile amount of no greater than about 3% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is a lubricant (e.g., a wax), whichfacilitates manufacture of metal closures and other fabricated coatedarticles by imparting lubricity to sheets of coated metal substrate.Preferred lubricants include, for example, Carnauba wax andpolyethylene-type lubricants. If used, a lubricant is preferably presentin the coating composition in an amount of at least about 0.1% byweight, and preferably no greater than about 2% by weight, and morepreferably no greater than about 1% by weight, based on the total solidsweight of the coating composition.

Another useful optional ingredient is an organosilicon material, such asa siloxane-based or polysilicone-based materials. Representativeexamples of suitable such materials are disclosed in PublishedInternational Application Nos. WO/2014/089410 A1 and WO/2014/186285 A1.

Another useful optional ingredient is a pigment, such as titaniumdioxide. If used, a pigment is present in the coating composition in anamount of no greater than about 70% by weight, more preferably nogreater than about 50% by weight, and even more preferably no greaterthan about 40% by weight, based on the total solids weight of thecoating composition.

The coating composition may also incorporate one or more optional curingagents (e.g., crosslinking resins, sometimes referred to as“crosslinkers”). The choice of particular crosslinker typically dependson the particular product being formulated. For example, some coatingsare highly colored (e.g., gold-colored coatings). These coatings maytypically be formulated using crosslinkers that themselves tend to havea yellowish color. In contrast, white coatings are generally formulatedusing non-yellowing crosslinkers, or only a small amount of a yellowingcrosslinker. Preferred curing agents are substantially free of or do notcontain each of BPA, BPF, BPS, and epoxy novolacs.

Any of the well-known, hydroxyl-reactive curing resins can be used. Forexample, phenoplast, blocked isocyanates, and aminoplast curing agentsmay be used, as well as combinations thereof. In addition, oralternatively, carboxyl-reactive curing resins may be used.

Phenoplast resins include the condensation products of aldehydes withphenols. Formaldehyde and acetaldehyde are preferred aldehydes. Variousphenols can be employed such as phenol, cresol, p-phenylphenol,p-tert-butylphenol, p-tert-amylphenol, and cyclopentylphenol.

Aminoplast resins are the condensation products of aldehydes such asformaldehyde, acetaldehyde, crotonaldehyde, and benzaldehyde with aminoor amido group-containing substances such as urea, melamine, andbenzoguanamine. Examples of suitable aminoplast crosslinking resinsinclude benzoguanamine-formaldehyde resins, melamine-formaldehyderesins, esterified melamine-formaldehyde, and urea-formaldehyde resins.One specific example of a suitable aminoplast crosslinker is the fullyalkylated melamine-formaldehyde resin commercially available from CytecIndustries, Inc. under the trademark CYMEL 303.

Examples of other generally suitable curing agents are the blocked ornon-blocked aliphatic, cycloaliphatic or aromatic di-, tri-, orpoly-valent isocyanates, such as hexamethylene diisocyanate (HMDI),cyclohexyl-1,4-diisocyanate, and the like. Further examples of generallysuitable blocked isocyanates include isomers of isophorone diisocyanate,dicyclohexylmethane diisocyanate, toluene diisocyanate, diphenylmethanediisocyanate, phenylene diisocyanate, tetramethyl xylene diisocyanate,xylylene diisocyanate, and mixtures thereof. In some embodiments,blocked isocyanates are used that have a number-average molecular weightof at least about 300, more preferably at least about 650, and even morepreferably at least about 1,000.

Other suitable curing agents may include benzoxazine curing agents suchas, for example, benzoxazine-based phenolic resins. Examples ofbenzoxazine-based curing agents are provided in U.S. Patent ApplicationPublication No. US 2016/0297994 A1.

Alkanolamide-type curing agents may also be used. Preferred such curingagents include beta-hydroxyalkyl-amide crosslinkers such as, forexample, those sold under the PRIMID trademark (e.g., the PRIMID XL-552and QM-1260 products) by EMS-CHEMIE AG.

The concentration of the curing agent (e.g., crosslinker) in the coatingcomposition may depend on the type of curing agent, the time andtemperature of the bake, and the molecular weights of the copolymerparticles. If used, the crosslinker is typically present in an amount ofup to about 50% by weight, preferably up to about 30% by weight, andmore preferably up to about 15% by weight. If used, the crosslinker istypically present in an amount of at least about 0.1% by weight, morepreferably at least about 1% by weight, and even more preferably atleast about 1.5% by weight. These weight percentages are based on thetotal resin solids weight of the coating composition.

In some embodiments, the coating composition may be cured without theuse of an external crosslinker (e.g., without phenolic crosslinkers).Additionally, the coating composition may be substantially free offormaldehyde and formaldehyde-containing materials, more preferablyessentially free of these compounds, even more preferably essentiallycompletely free of these compounds, and most preferably completely freeof or does not contain these compounds.

As mentioned above, in preferred embodiments the disclosed coatingcomposition is substantially free of or does not contain one or more of:(i) styrene and (ii) each of BPA, BPF, and BPS. In addition, the coatingcomposition is preferably substantially free of, completely free of ordoes not contain any structural units derived from a dihydric phenol, orother polyhydric phenol, having estrogenic agonist activity greater thanor equal to that of 4,4′-(propane-2,2-diyl)diphenol. More preferably,the coating composition is substantially free of, completely free of ordoes not contain any structural units derived from a dihydric phenol, orother polyhydric phenol, having estrogenic agonist activity greater thanor equal to that of BPS. In some embodiments, the coating composition issubstantially free of, completely free of or does not contain anystructural units derived from a bisphenol. By way of example, astructural unit derived from an epoxide of a bisphenol (e.g., adiglycidyl ether of a bisphenol) is considered to be a structural unitderived from a bisphenol.

Even more preferably, the coating composition is substantially free of,completely free of or does not contain any structural units derived froma dihydric phenol, or other polyhydric phenol, having estrogenic agonistactivity greater than 4,4′-(propane-2,2-diyl)bis(2,6-dibromophenol).Optimally, the coating composition is substantially free of, completelyfree of or does not contain any structural units derived from a dihydricphenol, or other polyhydric phenol, having estrogenic agonist activitygreater than 2,2-bis(4-hydroxyphenyl)propanoic acid. Estrogen agonistactivity may be evaluated using a suitable competent in vitro humanestrogen receptor assay such as the MCF-7 cell proliferation assay(“MCF-7 assay”) or other assay that may be used in place of orcorrelated to the MCF-7 assay through analysis of common referencecompounds. See, for example, U.S. Patent Application Publication No.2013/0316109 A1 for a discussion of such structural units and applicabletest methods.

In preferred embodiments, the coating composition is not prepared usinghalogenated monomers (whether free or polymerized), such as chlorinatedvinyl monomers. In further preferred embodiments, the coatingcomposition is substantially free of, completely free of or does notcontain halogenated monomers.

The coating composition may also optionally be rheologically modifiedfor different coating applications. For example, the coating compositionmay be diluted with additional amounts of the aqueous carrier to reducethe total solids content in the coating composition. Alternatively,portions of the aqueous carrier may be removed (e.g., evaporated) toincrease the total solids content in the coating composition. The finaltotal solids content in the coating composition may vary depending onthe particular coating application used (e.g., spray coating), theparticular coating use (e.g., for interior can surfaces), the coatingthickness, and the like.

If desired, the coating composition may also include one or more otheroptional polymers, such as, for example, one or more acrylic polymers,alkyd polymers, epoxy polymers, polyolefin polymers, polyurethanepolymers, polysilicone polymers, polyester polymers, and copolymers andmixtures thereof.

In some embodiments, such as for certain spray coating applications(e.g., inside spray for food or beverage cans including, e.g., aluminumbeverage cans), the coating composition may have a total solids weightgreater than about 5%, more preferably greater than about 10%, and evenmore preferably greater than about 15%, based on the total weight of thecoating composition. In these embodiments, the coating composition mayalso have a total solids weight less than about 40%, more preferablyless than about 30%, and even more preferably less than about 25%, basedon the total weight of the coating composition. In some of theseembodiments, the coating composition may have a total solids weightranging from about 18% to about 22%. The aqueous carrier may constitutethe remainder of the weight of the coating composition.

The aqueous carrier of the coating composition includes water and mayfurther include one or more optional organic solvents. In someembodiments, water constitutes greater than about 20% by weight, morepreferably greater than about 35% by weight, and even more preferablygreater than about 50% by weight of the total weight of the aqueouscarrier. In some embodiments, water constitutes 100% or less, morepreferably less than about 95% by weight, and even more preferably lessthan about 90% by weight of the total weight of the aqueous carrier.

While not intending to be bound by theory, the inclusion of a suitableamount of an organic solvent can be advantageous, in some embodiments(e.g., for certain coil coating applications to modify flow and levelingof the coating composition, control blistering, and maximize the linespeed of the coil coater). Accordingly, in certain embodiments, theorganic solvents may constitute greater than 0%, more preferably greaterthan about 5%, and even more preferably greater than about 10% by weightof the aqueous carrier, based on the total weight of the aqueouscarrier. In these embodiments, the organic solvents may also constituteless than about 80%, more preferably less than about 65%, and even morepreferably less than about 50% by weight of the aqueous carrier, basedon the total weight of the aqueous carrier. In some embodiments, organicsolvents constitutes less than 40% by weight of the aqueous carrier.

The coating composition preferably has a viscosity suitable for a givencoating application. In some embodiments, the coating composition mayhave an average viscosity greater than about 20 seconds, more preferablygreater than 25 seconds, and even more preferably greater than about 30seconds, based on the Viscosity Test described below (Ford Viscosity Cup#2 at 25° C.). In some embodiments, the coating composition may alsohave an average viscosity less than about 80 seconds, more preferablyless than 60 seconds, and even more preferably less than about 50seconds, based on the Viscosity Test described below (Ford Viscosity Cup#2 at 25° C.).

The coating composition of the present invention may be applied to avariety of different substrates using a variety of different coatingtechniques (e.g., spray coating, roll coating, wash coating, dipping,etc.). In preferred embodiments, the coating composition is applied asan inside spray coating to a container or portion or component thereof,or to a substrate surface that will become part or all of the inside ofsuch container. As briefly described above, cured coatings formed fromthe coating composition are particularly suitable for use on metal foodand beverage cans (e.g., two-piece cans, three-piece cans, and thelike). Two-piece cans (e.g., two-piece beer or soda cans and certainfood cans) are typically manufactured by a drawn and ironing (“D&I”)process, and are becoming increasingly prevalent within the food andbeverage industry. The cured coatings are also suitable for use in foodor beverage contact situations (collectively referred to herein as“food-contact”), and may be used on the inside or outside of such cans.

Preferred coating compositions of the present invention are particularlysuitable for in forming spray-applied interior coating on aluminum orsteel two-piece draw and ironed beverage or food cans.

The disclosed coating compositions may be present as a layer of amono-layer coating system or as one or more layers of a multi-layercoating system. The coating composition can be used as a primer coat, anintermediate coat, a top coat, or a combination thereof. The coatingthickness of a particular layer and of the overall coating system willvary depending upon the coating material used, the substrate, thecoating application method, and the end use for the coated article.Mono-layer or multi-layer coating systems including one or more layersformed from the disclosed coating composition may have any suitableoverall coating thickness, but will typically have an overall averagedry coating weight of from about 0.6 grams per square meter (“gsm”) toabout 13 gsm and more typically from about 1.0 gsm to about 6.5 gsm,with the chosen coating weight often depending on the desired end use.Minimum average dry film weights are also important to ensure adequatecoverage while still maintaining suitable coating performance. Forexample, for beverage cans, typical minimum dry film weights are about1.6 grams per square meter (gsm) (corresponding to a coating thicknessof about 1.4 micrometers or about 0.055 mils for a typical cured coatingdensity) for beer beverage cans; about 2.3 gsm (corresponding to about 2micrometers or about 0.079 mils) for soda cans; and about 3.4 gsm(corresponding to about 3 micrometers or about 0.117 mils) for canintended for use in packaging “hard-to-hold” products such as sports andenergy drinks, wine, mixers, and cocktail drinks. Coating systems foruse on closures (e.g., twist-off metal closures) for food or beveragecontainers may have an average total coating weight up to about 5.2 gsm(corresponding to about 4.6 micrometers or about 0.18 mils). For sprayedtinplate food cans, typical minimum dry film weights are about 5.4 gsm(corresponding to about 4.8 micrometers or about 0.19 mils). Minimum dryfilm weights for other applications may be about 7.9 gsm (correspondingto about 6.9 micrometers or about 0.27 mils), about 9.5 gsm(corresponding to about 8.4 micrometers or about 0.33 mils), and about11.7 gsm (corresponding to about 10.4 micrometers or about 0.41 mils).In certain embodiments in which the coating composition is used as aninterior coating on a drum (e.g., a drum for use with food or beverageproducts), a typical minimum dry film weight may be about 13 gsm(corresponding to about 11.7 micrometers or about 0.46 mils). However,for reasons including economy, cure speed and efficiency, the maximumdry coating weight for the various applications listed above may also beless than about 15 gsm (corresponding to about 13.5 micrometers or about0.53 mils).

The metal substrate used in forming rigid food or beverage cans, orportions thereof, typically has an average thickness in the range ofabout 125 micrometers to about 635 micrometers. Electro-tinplated steel,cold-rolled steel and aluminum are commonly used as metal substrates forfood or beverage cans, or portions thereof. In embodiments in which ametal foil substrate is employed in forming, e.g., a packaging article,the thickness of the metal foil substrate may be even thinner that thatdescribed above.

The disclosed coating compositions may be applied to a substrate eitherprior to, or after, the substrate is formed into an article such as, forexample, a food or beverage container or a portion thereof. In oneembodiment, a method of forming food or beverage cans, or portionsthereof, is provided that includes: applying a coating compositiondescribed herein to a metal substrate (e.g., applying the composition tothe metal substrate in the form of a planar coil or sheet), hardeningthe composition, and forming (e.g., via stamping) the substrate into apackaging container or a portion thereof (e.g., a food or beverage canor a portion thereof). For example, two-piece or three-piece cans orportions thereof such as riveted beverage can ends (e.g., soda or beercans) with a cured coating of the disclosed coating composition on asurface thereof can be formed in such a method. In another embodiment, amethod of forming food or beverage cans is provided that includes:providing a packaging container or a portion thereof (e.g., a food orbeverage can or a portion thereof), applying a coating compositiondescribed herein to the inside, outside or both inside and outsideportions of such packaging container or a portion thereof (e.g., viaspray application, dipping, etc.), and hardening the composition.

After applying the coating composition onto a substrate, the compositioncan be cured using a variety of processes, including, for example, ovenbaking by either conventional or convectional methods, or any othermethod that provides an elevated temperature suitable for curing thecoating. The curing process may be performed in either discrete orcombined steps. For example, substrates can be dried at ambienttemperature to leave the coating compositions in a largely uncrosslinkedstate. The coated substrates can then be heated to fully cure thecompositions. In certain instances, the disclosed coating compositionsmay be dried and cured in one step.

The cure conditions will vary depending upon the method of applicationand the intended end use. The curing process may be performed at anysuitable temperature, including, for example, oven temperatures in therange of from about 100° C. to about 300° C., and more typically fromabout 177° C. to about 250° C. If a metal coil is the substrate to becoated (e.g., metal coil for forming beverage can ends), curing of theapplied coating composition may be conducted, for example, by heatingthe coated metal substrate over a suitable time period to a peak metaltemperature (“PMT”) of preferably greater than about 177° C. Morepreferably, the coated metal coil is heated for a suitable time period(e.g., about 5 to 900 seconds) to a PMT of at least about 218° C. Thecured (viz., hardened) coating preferably is a continuous cured coating(viz., a coating that exhibits a suitably low initial metal exposurevalue, thereby indicating that the substrate has been effectivelycoated).

In some embodiments, the coating composition is an inside spray coatingcomposition capable of being spray applied on an interior of a food orbeverage can (e.g., a 2-piece food or beverage can) to effectively, andevenly, coat the substrate and form a continuous cured coating.

Preferred Tg values for the cured coating include those greater thanabout 50° C., more preferably greater than about 60° C., even morepreferably greater than about 70° C., and in some embodiments, greaterthan about 80° C. Preferred Tg values for the cured coating includethose less than about 120° C., more preferably less than about 115° C.,even more preferably less than about 110° C., and in some embodiments,less than about 100° C.

To further prevent or otherwise reduce coating penetration by anintended food or beverage product, the cured coating is preferablysuitably hydrophobic. For example, the cured coating can have a contactangle with deionized water greater than about 80, more preferablygreater than about 85, and even more preferably greater than about 90,when tested under ambient conditions. In some embodiments, the curedcoating may have a contact angle other than the above-referenced levels.

In some embodiments, the cured coating preferably exhibits desiredproperties for use as an interior food-contact coating (e.g., insidespray coating) for food and beverage containers. It consequently will bedesirable to avoid the use of materials that are unsuitable forfood-contact applications due to factors such as taste or toxicityconcerns or potential failure to meet governmental regulatoryrequirements. In addition, for such coatings it will be necessary toselect cure chemistries capable of imparting sufficient hardness andother relevant cured film properties during the relatively short ovencuring times employed when making food and beverage packaging containersand container components (e.g., less than about one minute for coilcoating, less than about two minutes or less than about one minute forinside spray beverage can coatings, and not more than 10 minutes forfood containers). These times are much shorter than those typicallyemployed for many other coating end uses. Also, such coatings will needto provide adequate performance at the very thin film weights andthicknesses employed for food and beverage coatings. These film weightsand thicknesses are often 1/10 or less of the film weights andthicknesses employed for many other coating end uses.

As a general guide to minimizing potential taste and toxicity concerns,cured food-contact coatings made from the disclosed multi-stage latexpreferably exhibit a global extraction value less than about 50 ppm,more preferably less than about 25 ppm, even more preferably less thanabout 10 ppm, and most preferably less than about 1 ppm, pursuant to theGlobal Extraction test below. These global extraction values aresufficiently stringent to exclude typical multi-stage latex coatingcompositions used for architectural paints and other residential orindustrial coating applications. Reduced Global Extraction values may beobtained by limiting the amount of mobile or potentially mobile speciesin the cured coating. Accordingly, normally it may be desirable to usepure rather than impure reactants; to avoid reaction schemes thatproduce unduly low yields or lead to undesirable side reactions; tochoose appropriate stoichiometry so as to limit the amounts of unreactedor unconsumed species including monomers, oligomers, initiators,crosslinkers and catalysts; to avoid the presence of readilyhydrolyzable species or bonds; to use the disclosed water-dispersiblepolymer for emulsion polymerizing the multi-stage latex rather thanusing conventional low molecular weight emulsion polymerizationsurfactants; to limit or avoid the use of other low molecular weightadjuvants (for example, low molecular weight antioxidants, biocides,buffers, coalescents, dispersing aids for pigments or colorants,defoamers, pH modifiers, nonaqueous solvents and cosolvents, and othermobile ingredients that sometimes accompany various coating adjuvants);and to ensure that thorough curing takes place within the planned curingcycle.

Additionally, the cured coating preferably exhibits a metal exposureless than about 5 milliamps (mA), more preferably less than about 2 mA,and even more preferably less than about 1 mA, pursuant to the InitialMetal Exposure test below. Reduced metal exposure values may be obtainedby forming a more flexible coating. For a conventional latex-basedcoating employing a single stage latex, typically there is a tradeoffbetween flexibility and resistance to flavor scalping. That is, acrylicsthat tend to have acceptable flexibility also tend to scalp flavorantsto an unsuitably high degree, whereas acrylics that tend to resistscalping flavorants to an unsuitable degree also tend to have unsuitableflexibility. This tradeoff in coating properties is particularlypronounced for acrylics made without using styrene. Without intending tobe bound by theory, it appears that the use in the present invention ofa multi-stage latex rather than a single stage latex may reduce theextent of such tradeoffs, thereby permitting attainment of satisfactoryflexibility together with adequate flavor scalping resistance, even foracrylics made without using styrene.

Flexibility is especially important for inside spray coatings, and formany other food or beverage can coatings, so that the coating candeflect with the metal substrate during post-cure fabrication steps(e.g., necking and dome reformation) and if the can is dropped from areasonable height during transport or use. In some preferredembodiments, the cured coating preferably exhibits a metal exposure lessthan about 10 mA, more preferably less than about 3.5 mA, even morepreferably less than about 2.5 mA, and optimally less than about 1.5 mA,pursuant to the Metal Exposure After Drop Damage test below.

The coating composition of the present disclosure also offers utility inother coating applications. These additional applications include, butare not limited to, wash coating, sheet coating, and side seam coatings(e.g., food can side seam coatings). Other commercial coatingapplication and curing methods are also envisioned, for example,electrocoating, extrusion coating, laminating, powder coating, and thelike. The coating composition may also be useful in medical or cosmeticpackaging applications, including, for example, on surfaces ofmetered-dose inhalers (“MDIs”), including on drug-contact surfaces.

Polymers and coating compositions such as those described in theExamples below may be evaluated using a variety of tests including:

1. Viscosity Test

This test measures the viscosity of a latex emulsion or coatingcomposition for rheological purposes, such as for sprayability and othercoating application properties. The test was performed pursuant to ASTMD1200-88 using a Ford Viscosity Cup #2 at 25° C. The results aremeasured in the units of seconds.

2. Curing Conditions

For beverage inside spray bakes, the curing conditions involvemaintaining the temperature measured at the can dome at 188° C. to 199°C. (measured at the can dome) for 55 seconds. For a food can insidespray bake, the curing conditions involve maintaining the temperature atthe can dome in a range of 208° C. to 218° C. for 2 minutes. Forbeverage end coil bakes, the curing conditions involve the use of atemperature sufficient to provide a peak metal temperature within thespecified time (e.g., 10 seconds at 204° C. means 10 seconds, in theoven, for example, and a peak metal temperature achieved of 204° C.).

3. Beverage can Inside Spray Testing

To facilitate spray-application of the disclosed coating compositions tothe interior of commercially available, preformed, aluminum D&I cans,the viscosity of each coating is reduced such that the flow rate of eachcoating through a Ford viscosity cup (#2 orifice) is in the range of20-80 seconds. This viscosity measurement is conducted with a clean,filtered sample of the coating composition at a temperature of 25° C.The tested cans are conventional 355 mL (12 U.S. fluid ounce) no. “211”diameter cans. The coating compositions are spray-applied at 115milligrams (dry weight) per can coating weight using a laboratory scaleD&I spray unit commercially available from Reynolds DG-250. Thislaboratory unit is considered an effective replica of commercial D&Ibeverage can spray units. The applied coatings are cured at 188° C. to199° C. (measured at the can dome) for 55 seconds using alaboratory-scale D&I can oven commercially available from Ross Co.

4. Food Can Inside Spray Testing

To facilitate spray-application of the disclosed coating compositions tothe interior of commercially available, preformed, tinplate D&I cans,the viscosity of each coating is reduced such that the flow rate of eachcoating through a Ford viscosity cup (#2 orifice) is in the range of20-80 seconds. This viscosity measurement is conducted with a clean,filtered sample of the coating composition at a temperature of 25° C.The test cans have a “300×407” commercial designation, corresponding toa 0.113 m height, 0.076 m diameter and 0.032 m² internal area. Thetested cans include conventional sidewall beading which imparts improvedcrush resistance to the can. In addition, each can is flanged, whichallows for effective seaming and closure of the can with an appropriate300 diameter commercially available food can end. The coatingcompositions are spray-applied at 250 to 375 milligrams (dry weight) percan coating weight using a laboratory scale D&I spray unit commerciallyavailable from H. L. Fisher Co. This laboratory unit is considered aneffective replica of commercial D&I food can spray units. The appliedcoatings are cured at 208° C. to 218° C. (measured at the can) for 2minutes using a laboratory-scale D&I can oven commercially availablefrom Ross Co.

5. Initial Metal Exposure

This test method, sometimes called an “Enamel Rater Test”, evaluates thecoverage and integrity of a dry coating on the inside of a can bymeasuring current flow through the can and an electrolyte. A can isfilled with an electrolyte and an electrode is lowered into thesolution. A constant voltage is applied and the resulting current ismeasured in milliamps. The voltage level, time of exposure andelectrolyte solution can all be varied as needed, and may be differentdepending upon factors including the packaging facility or packaging enduse. In a representative procedure, an interior “inside spray” coatingis applied using a high pressure airless spray and minimum dry filmweights of 1.6 grams per square meter (gsm) for a beer can; 2.3 gsm fora soda can; 3.4 gsm for a can intended for use in packaging a“hard-to-hold” beverage product such as a sports drink, energy drink,wine, mixer, or cocktail; and 5.4 gsm for an inside spray coatedtinplate food can.

The coated cans are filled with a room temperature electrolyte solutioncontaining 1 wt. % sodium chloride in deionized water, and an electricalprobe is attached to an uncoated, electrically conducting portion on theoutside of the can. A second probe is immersed inside the can in themiddle of the electrolyte solution. A 6.3 VDC constant voltage isapplied continuously for four seconds and the average current ismeasured in milliamps using a WACO Enamel Rater II supplied by TheWilkens-Anderson Company or similar tester. If any uncoated metal ispresent on the inside of the can, a current is passed between these twoprobes and is displayed by the tester. The observed current is directlyproportional to the amount of metal that has not been effectivelycovered with coating. The goal is to achieve 100% coating coverage onthe inside of the can, which would result in a 0 mA metal exposurevalue. Preferred coatings give metal exposure values of less than 3 mA,more preferred values of less than 2 mA, and even more preferred valuesof less than 1 mA. Commercially acceptable metal exposure values aretypically less than 2 mA on average.

6. Metal Exposure after Drop Damage

Drop damage resistance measures the ability of the coated container toresist cracks after being in conditions simulating dropping of a filledcan, and may be used for both beverage and food containers. The presenceof cracks is measured by passing electrical current via an electrolytesolution, as previously described in the Initial Metal Exposure section.A coated container is filled with the electrolyte solution (1% NaCl indeionized water) and the initial metal exposure is recorded. Theelectrolyte solution is removed and the can is then filled withroom-temperature tap water. For “inside spray” beverage or food cans,the film weights described in the Initial Metal Exposure test can beused.

The water-filled can, which does not include a “top” can end, is droppedthrough a cylindrical tube having a 2 and ⅞ inch (7.3 centimeter)internal diameter, can bottom down, onto an impact wedge (e.g., aninclined plane angled upwards at 33 degrees). The impact wedge ispositioned relative to the tube such that a dent is formed in the rimarea where the can bottom end meets the sidewall (typically referred toas the “chime” of a beverage can). The water-filled can is droppedthrough the tube from a 24-inch (61 centimeter) height (as measuredbetween the can bottom and the point of impact on the impact wedge) ontoan inclined plane, causing a dent in the chime area. The can is thenturned 180 degrees, and the process is repeated.

Water is then removed from the can and metal exposure is again measuredas described above. If there is no damage, no change in current (mA)will be observed relative to the Initial Metal Exposure value.Typically, an average of 6 or 12 container runs is recorded. The metalexposures results for before and after the drop are reported as absolutevalues. The lower the milliamp value, the better the resistance of thecoating to drop damage. Preferred coatings give metal exposure valuesafter drop damage of less than 10 mA, more preferred values of less than3.5 mA, even more preferred values of less than 2.5 mA, and optimalvalues of less than 1.5 mA.

Drop damage is often reported as a “delta” or “A” mA value, which is thedifference in the measured current passage (“metal exposure”) after theDrop Damage test relative to the initial measured current passage priorto drop damage (measured using the Initial Metal Exposure test above).Little (e.g., <1 mA) to no change in the measured current passage is anindication that the coating possesses good flexibility for the end use.In the Example Section below, the drop damage A values reported inTables 3 and 4 were conducted using standard 12 ounce (355 mL)211-diameter aluminum beverage cans using an inside spray coating dryfilm weight of 4.0 gsm (which corresponds to 115 mg/can).

7. Necking Test

This test measures the flexibility and adhesion of the film followingcommercial necking process. Necking is done to facilitate theapplication of a container end that allows sealing the container, and iscommonly performed on beverage cans. The test involves applying thecoating to the container at a recommended film thickness and subjectingthe container to a recommended bake (see above can, coating, and bakespecifications for items 2-4). Prior to the necking process, sample canstypically will have a metal exposure value of <1.0 mA (average of 12cans) when evaluated using an electrolyte solution as described above.After the necking process, cans should display no increase in metalexposure compared to the average for 12 non-necked cans. Elevated mAvalues indicate a fracture in the film which constitutes film failure.

8. Adhesion

Adhesion testing is performed to assess whether the coating adheres tothe coated substrate. The adhesion test was performed according to ASTMD 3359—Test Method B, using SCOTCH 610 tape, available from 3M Companyof Saint Paul, Minn.

Adhesion is generally rated on a scale of 0-10 where a rating of “10”indicates no adhesion failure (best), a rating of “9” indicates 90% ofthe coating remains adhered, a rating of “8” indicates 80% of thecoating remains adhered, and so on. Adhesion ratings of 10 are typicallydesired for commercially viable coatings.

9. Blush Resistance

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount ofsolution (e.g., water) absorbed into a coated film. When the filmabsorbs water, it generally becomes cloudy or looks white. Blush isgenerally measured visually using a scale of 0-10 where a rating of “10”indicates no blush (best) and a rating of “0” indicates completewhitening of the film (worst). Blush ratings of 7 or higher aretypically desired for commercially viable coatings, and optimally 9-10.

10. Corrosion Resistance

These tests measure the ability of a coating to resist attack bysolutions of different levels of aggressiveness. Briefly, a givencoating is subjected to a particular solution, as described below, andthen measured for adhesion and blush resistance, each also describedbelow. For each test, a result is given using a scale of 0-10, based onthe Adhesion Resistance, Blush Resistance, or Blush Adhesion Resistance,where a rating of “10” is best and a rating of “0 is worst.

A. Deionized Water

Deionized water is heated to 82° C. Coated panels are immersed in theheated solution for 30 minutes and then removed, rinsed, and dried.Samples are then evaluated for adhesion and blush, as previouslydescribed.

B. Acetic Acid Solution

A 3% solution of acetic acid (C₂H₄O₂) in deionized water is prepared andheated to 100° C. Coated panels are immersed in the heated solution for30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

C. Citric Acid Solution

A 2% solution of citric acid (C₆H₈O₇) in deionized water is prepared andheated while subjected to a pressure sufficient to achieve a solutiontemperature of 121° C. Coated panels are immersed in the heated solutionfor 30 minutes and then removed, rinsed, and dried. Samples are thenevaluated for adhesion and blush, as previously described.

11. Pasteurization

The pasteurization test determines how a coating withstands theprocessing conditions for different types of food products packaged in acontainer. Typically, a coated substrate is immersed in a water bath andheated for 5-60 minutes at temperatures ranging from 65° C. to 100° C.For the present evaluation, the coated substrate was immersed in eithera deionized water bath for 45 minutes at 85° C., or a 3% solution ofacetic acid (C₂H₄O₂) in deionized water for 30 minutes at 100° C. Thecoated substrate is then removed from the bath and tested for coatingadhesion and blush as described above. Commercially viable coatingspreferably provide adequate pasteurization resistance with perfectadhesion (rating of 10) and blush ratings of 5 or more, optimally 9-10.

12. Glass Transition Temperature (“Tg”)

Samples for DSC testing may be prepared by first applying the liquidresin composition onto aluminum sheet panels. The panels are then bakedin a Fisher ISOTEMP electric oven for 20 minutes at 300° F. (149° C.) toremove volatile materials. After cooling to room temperature, thesamples are scraped from the panels, weighed into standard sample pansand analyzed via DSC using a standard heat-cool-heat method. The samplesare equilibrated at −60° C., then heated at 20° C. per minute to 200°C., cooled to −60° C., and then heated again at 20° C. per minute to200° C. Glass transitions are calculated from the thermogram of the lastheat cycle. The glass transition is measured at the inflection point ofthe transition.

13. Flavor Scalping

Flavor scalping may be assessed as described in Published InternationalApplication. No. WO 2018/013766 A1 entitled “Latex Coating CompositionHaving Reduced Flavor Scalping Properties.” The amounts of each aldehydelost from a test solution during storage are measured and calculated asa percent of the original concentration. Flavor Scalping is reported asthe % aldehyde lost relative to a current industry standard coatingformulation, with high reported percentage values being preferred overlow percentage values.

14. Global Extraction

The global extraction test is designed to estimate the total amount ofmobile material that can potentially migrate out of a coating and intofood packed in a coated can. Typically, a coated substrate is subjectedto water or solvent blends under a variety of conditions to simulate agiven end use. Acceptable extraction conditions and media can be foundin 21 CFR § 175.300 paragraphs (d) and (e). The allowable globalextraction limit as defined by the FDA regulation is 50 parts permillion (ppm). The extraction procedure used in the current invention isdescribed in 21 CFR § 175.300 paragraph (e)(4)(xv) with the followingmodifications to ensure worst-case scenario performance: (1) the alcohol(ethanol) content was increased to 10% by weight, and (2) the filledcontainers were held for a 10-day equilibrium period at 37.8° C. (100°F.). These conditions are per the FDA publication “Guidelines forIndustry” for preparation of Food Contact Notifications.

The coated beverage can is filled with 10% by weight aqueous ethanol andsubjected to pasteurization conditions (65.6° C., 150° F.) for 2 hours,followed by a 10-day equilibrium period at 37.8° C. (100° F.).Determination of the amount of extractives is determined as described in21 CFR § 175.300 paragraph (e) (5), and ppm values were calculated basedon surface area of the can (no end) of 44 square inches with a volume of355 milliliters. Preferred coatings give global extraction results ofless than 50 ppm, more preferred results of less than 10 ppm, and evenmore preferred results of less than 1 ppm. Most preferably, the globalextraction results are optimally non-detectable.

For materials that have not previously been used as packaging coatingson food or beverage containers (e.g., for architectural or industrialcoating materials), it can be difficult to use the above procedures tomeasure global extraction, as the coating material might not previouslybeen applied at the low coating weights and low viscosities typicallyrequired for food and beverage packaging coatings. Also, the coatingmaterial might not have previously been thermally cured using the ovencuring procedures typically employed for food and beverage coatings. Insuch cases the material may instead be evaluated by applying thematerial to a beverage can as described above, but using a coatingweight and viscosity as disclosed or recommended for its existing use(e.g., its architectural or industrial use), followed by drying orotherwise hardening the coating as disclosed or recommended for itsexisting use and then within an hour after the material reaches atack-free state subjecting the dried coating to the above-mentioned 21CFR § 175.300 paragraph (e)(4)(xv) extraction procedure with theabove-described worst-case scenario modifications. For example, for alatex wall paint containing a multi-stage latex, global extraction mayneed to be determined by applying the paint using the paintmanufacturer's recommended spray painting procedure and viscosity,air-drying the applied coating and then performing the extractionprocedure within an hour after the coating reaches a tack-free state.Wall paints and other industrial coatings that are so applied, dried andevaluated may exceed the recited 50 ppm global extraction limit due tofactors such as incomplete cure and the presence of extractable speciessuch as cosolvents, low molecular weight surfactants, coalescents andother coating material adjuvants.

EXAMPLES

The present disclosure is more particularly described in the followingexamples that are intended as illustrations only, since numerousmodifications and variations within the scope of the present disclosurewill be apparent to those skilled in the art. Unless otherwiseindicated, all parts and percentages are by weight. Unless indicatedotherwise, the test methods described above were used to generate thedata included in the below Tables.

Example 1 Preformed Acrylic A

A monomer premix of 197.35 parts glacial methacrylic acid (MAA), 59.28n-butyl methacrylate (BMA), 88.88 parts ethyl methacrylate (EMA), 44.45parts ethyl acrylate (EA), 113.36 parts butanol and 12.63 partsdeionized (“DI”) water was prepared in a separate vessel. An initiatorpremix of 18.54 parts LUPEROX 26 initiator and 41.63 parts n-butanol(“butanol”) was prepared in a separate vessel. A reactor was equippedwith an agitator, reflux condenser, and thermocouple, capable of beingheated and cooled and blanketed or sparged with inert gas or nitrogen.To the reactor, 141.39 parts butanol and 6.94 parts deionized water wereadded. With agitation on and the vessel being blanketed with inert gas,the contents were heated to 97° C. Once at temperature, 1.03 partsLUPEROX 26 initiator were added and the batch held for 5 minutes. After5 minutes, the monomer premix and the remaining initiator premix wereadded to the vessel over a two hour period while maintaining thereactants at 97° C. to 100° C. When the addition was complete, 18.06parts butanol was used to rinse the monomer premix vessel to the reactorand 6.03 parts butanol was used to rinse the initiator premix vessel tothe reactor. The batch was held at 98° C. to 99° C. for 30 minutes afterwhich 1.85 parts LUPEROX 26 initiator were added and rinsed with 1.86parts butanol. The batch was held at 98° C. for 60 minutes after which asecond addition of 1.85 parts LUPEROX 26 were added and rinsed with 1.86parts butanol. The batch was held at 98° C. to 100° C. for two hours.After the two hour hold, 235.78 parts butyl cellosolve and 7.26 partsdeionized water were added and the reactor contents cooled beforeremoving from the reactor. The resulting acrylic pre-polymer gives apolymer with a monomer ratio (weight parts) of methacrylic acid/butylmethacrylate/ethyl methacrylate/ethyl acrylate at 50.6/15.2/22.8/11.4and a Fox equation calculated Tg of 90° C. The butanol to ButylCellosolve ratio was 58/42 by weight. The solids content was ˜40.3% withan acid number of ˜312 mg KOH/g resin and a viscosity of 7700centipoise.

Example 2 Preformed Acrylic B

Using the process described above for Example 1, a second preformedacrylic was prepared using a monomer weight ratio of methacrylicacid/butyl methacrylate/methyl methacrylate (MMA)/ethyl acrylate at60/15/10/15 and a Fox equation calculated Tg of 100° C. The butanol toButyl Cellosolve ratio was adjusted to 76/24 by weight. The solidscontent was ˜38.6% with an acid number of ˜384 mg KOH/g resin and aviscosity of 28,000 centipoise.

Example 3 Water-Based Polyether-Acrylate Copolymer Base Dispersion

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen and vacuum, the following were added:1204.12 parts of the diglycidyl ether of tetramethyl bisphenol F, 295.1parts hydroquinone, 0.71 parts ethyltriphenyl phosphonium iodide, 35.23parts carbitol, and 131.36 parts butyl cellosolve. (Suitablepreparations of the diglycidyl ether of tetramethyl bisphenol F aredescribed, for example, in WO 2017079437 A1.) With agitation on and thevessel being blanketed with inert gas, the contents were heated to 155°C. The system was allowed to exotherm to 181° C. when vacuum was appliedto create a reflux to control the peak temperature to a maximum of ˜194°C. Once the peak temperature was achieved a 30 minute hold began and thetemperature was allowed to drift down and the pressure was returned toatmospheric pressure. After the 30 minute hold, 0.08 partsethyltriphenyl phosphonium iodide were added. After one hour from thepeak temperature samples were taken every 30 minutes until an epoxyvalue of 0.039 equivalents per 100 gram solid resin was achieved. At thedesired epoxy value, 144.15 parts butyl cellosolve and 64.15 parts hexylcellosolve were added and the temperature allowed to drift down. Then1617.58 parts of the Preformed Acrylic A of Example 1 were added. Oncein, the material was rinsed in with 92.98 parts butyl cellosolve. Thecontents were mixed for 30 minutes while the temperature was adjusted to99° C. After 30 minutes, 194.43 parts deionized water were added and thetemperature adjusted to 93° C. At temperature, 142.87 parts of dimethylethanol amine (“DMEOA”) were added over 5 minutes. The batch was thenheld at 96° C. to 101° C. for one hour. At the end of the hour, anyexternal heat was turned off, the agitation increased and 1982.62 partsof deionized water were added uniformly over 50 minutes. After the waterwas in, another 2768.62 parts of deionized water were added over 30minutes. Once all the water was in, the batch was held 30 minutes toassure uniformity. This produced a water based dispersion of thepolyether-acrylate copolymer having 23.9% solids, 88.7 mg KOH/g resinacid number, 6.52 pH, 0.17 micron particle size and 35 second #4 Fordviscosity.

Example 4 Alternate Water-Based Polyether-Acrylate Copolymer BaseDispersion

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen and vacuum begin able to be applied,the following were added: 1202.92 parts of the diglycidyl ether oftetramethyl bisphenol F, 289.64 parts hydroquinone, 0.71 partsethyltriphenyl phosphonium iodide, and 165.84 parts butyl cellosolve.With agitation on and the vessel being blanketed with inert gas, thecontents were heated to 145° C. The system was allowed to exotherm to184° C. Once the peak temperature was achieved a 30 minute hold beganand the temperature was allowed to drift down. After the 30 minute hold,0.08 parts ethyltriphenyl phosphonium iodide were added. After one hourfrom the peak temperature samples were taken every 30 minutes until anepoxy value of 0.039 equivalents per 100 gram solid resin was achieved.At the desired epoxy value, 236.04 parts butyl cellosolve and 63.9 partshexyl cellosolve were added and the temperature allowed to drift down.Then 1964.03 parts of the preformed Acrylic B of Example 2 were added.The contents were mixed for 15 minutes, then 121.25 parts deionizedwater were added. The batch was mixed for 5 additional minutes, then174.25 parts of dimethyl ethanol amine were added over 5 minutes. Thebatch was then held at 98° C. to 101° C. for 90 minutes. At the end ofthe 90 minute hold, any external heat was turned off, the agitationincreased and 1973.91 parts of deionized water were added uniformly over50 minutes. After the water was in, another 3807.40 parts of deionizedwater were added over about 40 minutes. Once all the water was in, thebatch was held 30 minutes to assure uniformity. This produced a waterbased dispersion having 23.1% solids, 113.6 mg KOH g/resin acid number,6.52 pH, and 9100 centipoise viscosity.

Comparative Example 5 Water-Based Polyether-Acrylate CopolymerDispersion with a Single-Stage Emulsion Polymerization Extension

The contents of the reactor in Example 3 were heated to 85° C. Attemperature, 373.9 parts butyl methacrylate, 467.79 parts ethylmethacrylate, and 93.34 parts butyl acrylate were added over ˜60minutes. The monomers used were butyl methacrylate/ethylmethacrylate/butyl acrylate at a weight ratio of 40/50/10 with a Foxequation calculated Tg of 30° C. When the monomer addition was complete,the residual monomer mixture was rinsed into the reactor using 345.56parts deionized water. With the contents of the reactor at 82° C., 7.33parts benzoin and 7.33 parts 34% hydrogen peroxide were added and rinsedinto the reactor with 7.59 parts deionized water. The batch was held fortwo hours and allowed to increase in temperature to 88° C. After the twohours, 2.0 parts benzoin and 2.0 parts 34% hydrogen peroxide were addedand rinsed into the reactor with 7.59 parts deionized water. The batchwas held one hour after which 2.0 parts benzoin and 2.0 parts 34%hydrogen peroxide were added and rinsed into the reactor with 7.59 partsdeionized water. The batch was held at temperature for one hour and thencooled. This produced a water-based dispersion at 30.8% Solids, 63.0acid number, 6.42 pH, 0.21 micron average particle size and 73 seconds#4 Ford viscosity.

Example 6 Water-Based Polyether-Acrylate Copolymer Dispersion with aMulti-Stage Emulsion Polymerization Extension for Reduced PolyetherContent

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen, 714.34 parts of Example 5 and 189.04parts deionized water were added. With agitation on and the vesselblanketed with inert gas, the material was heated to 75° C. to 82° C. Attemperature, 8.78 parts butyl methacrylate, 74.43 parts ethylmethacrylate, and 4.35 parts butyl acrylate were added. This was amonomer blend of butyl methacrylate/ethyl methacrylate/butyl acrylate ata weight ratio of 10/85/5 with a Fox equation calculated Tg of 51° C.When the monomer addition was complete, the residual monomer mixture wasrinsed into the reactor using 4.52 parts deionized water. With thecontents of the reactor at 82° C., 0.73 parts benzoin and 0.73 parts 34%hydrogen peroxide were added and rinsed into the reactor with 0.76 partsdeionized water. The batch was held for two hours and allowed toincrease in temperature to 85° C. After the two hours, 0.20 partsbenzoin and 0.20 parts 34% hydrogen peroxide were added and rinsed intothe reactor with parts 0.76 deionized water. The batch was held one hourafter which 0.20 parts benzoin and 0.20 parts 34% hydrogen peroxide wereadded and rinsed into the reactor with 0.76 parts deionized water. Thebatch was held at temperature for one hour and then cooled. Thisproduced a water-based dispersion having 30.7% Solids, 43.2 acid number,6.48 pH, a 0.22 micron average particle size and a 21 seconds #4 FordViscosity.

Examples 7-9 Additional Multi-Stage Latex Containing Resin Systems

Three additional resin system examples (viz., Examples 7-9) wereprepared using the method described in Example 6. Similar to Example 6,the resin systems of Examples 7-9 were prepared by emulsion polymerizinga higher Tg stage (“Stage 2”) in the presence of the single stage latexof Comparative Example 5 to yield a resin system including a multi-stagelatex. Table 1 below compares these systems and Example 6 relative toComparative Example 5, which includes only a single emulsion polymerizedstage and a higher polyether level. Unless indicated otherwise, theamounts in Table 1 are all weight parts. The weight contribution of thepolyether polymer portions and acrylic polymer portions present in thewater-based polyether-acrylate copolymer dispersions used to make theparticular latexes are indicated separately as “Overall % Polyether” and“% Preformed Acrylic.” The weight contribution of each of the firstemulsion polymerized stage and the second emulsion polymerized stage arereferred to, respectively, as “% Stage 1” and “% Stage 2”. The overallpercentage of polymerized ethylenically unsaturated monomers (viz., thecontribution from the preformed acrylic and the single stage ormulti-stage latex is reported as the “Overall % Acrylic”. In Examples6-9, Stage 1 corresponds to the lower Tg emulsion polymerized stage,Stage 2 corresponds to the higher Tg emulsion polymerized stage, and thelower Tg stage was emulsion polymerized before the higher Tg stage.

TABLE 1 Comparative Example 5 Example 6 Example 7 Example 8 Example 9Overall % Polyether 49 35 35 35 35 % Preformed Acrylic 21 15 15 15 15 %Stage 1 30   21.4   21.4   21.4   21.4 % Stage 2  0   28.6   28.6   28.6  28.6 Wt. Ratio Stage 1: Stage 2 100:0 43:57 43:57 43:57 43:57 Stage 1Monomer Wt. Ratios EMA 50 EMA 50 EMA 50 EMA 50 EMA 50 BMA 40 BMA 40 BMA40 BMA 40 BMA 40 BA 10 BA 10 BA 10 BA 10 BA 10 Stage 1 Tg 30° C. 30° C.30° C. 30° C. 30° C. Stage 2 Monomer Wt. Ratios NA EMA 85 EMA 25 EMA 10EMA 0 BMA 10 BMA 35 BMA 30 BMA 20 BA 5 BA 5 BA 5 BA 5 MMA 0 MMA 35 MMA55 MMA 75 Stage 2 Tg NA 51° C. 51° C. 60° C. 72° C. Delta Tg NA 21° C.21° C. 30° C. 42° C. Overall % Acrylic 51 65 65 65 65 % Solids   30.8%  30.7%   30.5%   30.6%   30.4% Acid Number (mg KOH/g resin) 63   43.2  43.8   43.3   44.7 pH   6.4   6.5   6.5   6.5   6.5 Average ParticleSize (micrometers)    0.21    0.22    0.22    0.23    0.23 Viscosity (#4Ford)  73″  21″  20″  19″  19″

Resin System Examples 10-19 Additional Multi-Stage Latex-ContainingResin Systems

The following process was used to produce the resin systems of each ofExamples 10 to 19. The indicated amounts were those used to produceExample 13. The amounts of each of the ingredients used in the remainingExamples 10-12 and 14-19 are shown below in Table 2 along with theExample 13 amounts. As shown in Table 2, adjustments were made to thevarious examples to provide different monomer ratios, different polymerTg's and different ratios of Stage 2 to Stage 1.

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen, 399.5 parts of the Example 4copolymer and 114.0 parts deionized water were added. With agitation onand the vessel blanketed with inert gas, the mixture was heated to 81°C. At temperature, 16.25 parts butyl methacrylate, 16.25 parts butylacrylate, and 9.0 parts methyl methacrylate were added. This is amonomer blend of butyl methacrylate/butyl acrylate/methyl methacrylateat a ratio of 39/39/22 with a Fox equation calculated Tg of −2° C. Whenthe monomer addition was complete, the residual monomer mixture wasrinsed into the reactor using 31.25 parts deionized water. With thecontents of the reactor at 82° C., 0.75 parts benzoin were rinsed intothe reactor with 35.0 parts deionized water. The batch was heated to 82°C. and 0.75 parts 34% hydrogen peroxide were added. The batch was heldfor one hour and allowed to increase in temperature to 88° C. After theone hour hold, the conversion of monomer to polymer was determined to be93%. After another hour hold, a sample was taken and 75 parts deionizedwater were added to the reactor. The sample was determined to have 95%of the monomer converted to polymer. The batch was heated to 82° C. anda monomer blend of 11.87 parts butyl methacrylate, 5.87 parts butylacrylate, and 100.75 parts methyl methacrylate was added. This blend hasbutyl methacrylate/butyl acrylate/methyl methacrylate at a ratio of10/5/85 with a Fox equation calculated Tg of 82° C. When the monomeraddition was complete, the residual monomer mixture was rinsed into thereactor using 81.25 parts deionized water. Then 0.87 parts benzoin and0.87 parts 34% hydrogen peroxide were added and rinsed into the reactorwith parts 37.0 deionized water. The batch was held one hour after which0.12 parts benzoin and 0.12 parts 34% hydrogen peroxide were added andrinsed into the reactor with 7.37 parts deionized water. The batch washeld at temperature for 90 minutes. Then 0.12 parts benzoin and 0.12parts 34% hydrogen peroxide were added and rinsed into the reactor with7.37 parts deionized water. The batch was held for 2 hours and thencooled. This gave material at 30.0% solids, 35.8 mg KOH/g resin acidnumber and 0.34 micron average particle size.

Table 2 below compares the compositional makeup of the resin systems ofExamples 10-19. Unless indicated otherwise, the amounts in Table 2 areall weight parts. In Table 2, the weight contribution of the polyetherpolymer portions and acrylic polymer portions are shown using the samenomenclature employed in Table 1. In Examples 10-19, Stage 1 correspondsto the lower Tg emulsion polymerized stage, Stage 2 corresponds to thehigher Tg emulsion polymerized stage, and the lower Tg stage wasemulsion polymerized before the higher Tg stage.

TABLE 2 Ex. 10 Ex. 11 Ex. 12 Ex. 13 Ex. 14 % Polyether 20 20 20 20 20 %Preformed 10.6 10.6 10.6 10.6 10.6 Acrylic % Stage 1 30 21.4 21.4 3021.4 % Stage 2 39.4 48 48 39.4 48 Overall % 80 80 80 80 80 Acrylic Wt.Ratio 43:57 31:69 31:69 43:57 31:69 Stage 1:Stage 2 Stage 1 Monomer BMA42 BMA 72 BMA 42 BMA 72 BMA 72 Wt. Ratios MMA 40 MMA 10 MMA 40 MMA 10MMA 10 BA 18 BA 18 BA 18 BA 18 BA 18 Stage 1 Tg 29° C.  9° C. 29° C.  9°C.  9° C. Stage 2 Monomer BMA 32 BMA 32 BMA 10 BMA 10 BMA 10 Wt. RatiosMMA 63 MMA 63 MMA 85 MMA 85 MMA 85 BA 5  BA 5  BA 5  BA 5  BA 5  Stage 2Tg 62° C. 62° C. 82° C. 82° C. 82° C. Delta Tg 33° C. 53° C. 53° C. 73°C. 73° C. % Solids 39.9% 30.0% 30.2% 30.0% 29.9% Acid Number 35.8 35.235.0 35.8 35.6 (mg KOH/ g resin) Average 0.32 0.34 0.35 0.34 0.35Particle Size (micrometers) Ex. 15 Ex. 16 Ex. 17 Ex. 18 Ex. 19 %Polyether 20 20 20 20 20 % Preformed 10.6 10.6 10.6 10.6 10.6 Acrylic %Stage 1 25 30 21.4 30 25 % Stage 2 44.4 39.4 48 39.4 44.4 Overall % 8080 80 80 80 Acrylic Wt. Ratio 36:64 43:57 31:69 43:57 36:64 Stage1:Stage 2 Stage 1 Monomer BMA 57 BMA 42 BMA 42 BMA 72 BMA 57 Wt. RatiosMMA 25 MMA 40 MMA 40 MMA 10 MMA 25 BA 18 BA 18 BA 18 BA 18 BA 18 Stage 1Tg 19° C. 29° C. 29° C.  9° C. 19° C. Stage 2 Monomer BMA 20 BMA 10 BMA32 BMA 32 BMA 20 Wt. Ratios MMA 75 MMA 85 MMA 63 MMA 63 MMA 75 BA 5  BA5  BA 5  BA 5  BA 5  Stage 2 Tg 72° C. 82° C. 62° C. 62° C. 72° C. DeltaTg 53° C. 53° C. 33° C. 53° C. 53° C. % Solids 29.7% 29.7% 29.9% 29.9%29.9% Acid Number 35.0 35.5 35.0 35.0 35.2 (mg KOH/ g resin) Average0.31 0.32 Particle Size (micrometers)

Finish Examples 6-9 Inside Spray Coating Compositions

Inside spray beverage can coating compositions were formulated using theresin systems of each of Comparative Example 5 and Examples 6-9. Theresulting inside spray coating compositions are indicated below in Table3 as “Finish” Examples 6-9 and certain coating performancecharacteristics are reported in comparison to an inside spray coatingcomposition made using Comparative Example 5. The particular FinishExample numbers correspond to the indicated resin system incorporatedinto the inside spray coating composition.

TABLE 3 Comparative Finish Finish Finish Finish Finish Example 5 Example6 Example 7 Example 8 Example 9 Comparative  63.7  63.8  64.2  64.1 64.5 Example 5 Example 6 0  63.8 0 0 0 Example 7 0 0  64.2 0 0 Example8 0 0 0  64.1 0 Example 9 0 0 0 0  64.5 DI Water  30.1  27.4  27.0  27.2 26.8 Butyl Cellosolve   2.7   4.1   4.1   4.1   4.1 Amy Alcohol   3.4  3.4   3.4   3.4   3.4 Butyl Alcohol 0   1.1   1.1   1.1   1.1 DMEOA AsNeeded As Needed As Needed As Needed As Needed Formulated %  20.5  20.5 20.5  20.5  20.5 Non-Volatiles Viscosity 36″ 43″ 41″ 41″ 39″ DropDamage Δ (mA)   0.2   0.4   0.5   0.1   0.1 Measured Tgs (° C.) 44/10645/102 61/103 40/70/102 39/79/103 Scalping, % 96  77  87  89  92  CitricBlush SW 10  6 6 6 6

For Comparative Finish Example 5, two Tg values were observed, with the44° C. value being attributable to the single stage latex, and the 106°C. value being attributable to the polyether-acrylate copolymerdispersion.

As in Table 3, inside spray beverage can coating compositions were alsoformulated using the resin systems of each of Examples 10-19. Theresulting inside spray coating compositions are indicated below in Table4 as “Finish” Examples 10-19 and certain coating performancecharacteristics are reported. The particular Finish Example numberscorrespond to the indicated resin system incorporated into the insidespray coating composition.

TABLE 4 Finish Example 10 11 12 13 14 15 16 17 18 19 Polymer 65.6  65.4 64.9  65.4  65.6  66.0  66.0  65.6  65.6  65.6  % Polyether 20   20  20   20   20   20   20   20   20   20   % Acrylic 80   80   80   80  80   80   80   80   80   80   DI Water 23.6  23.8  24.2  23.6  23.6 23.2  23.2  23.6  23.6  23.6  Butyl 5.4 5.4 5.4 5.4 5.4 5.4 5.4 5.4 5.45.4 Cellosolve Amy 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.4 Alcohol Butyl1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Alcohol DMEOA As As As As As AsAs As As As needed needed needed needed needed needed needed neededneeded needed Formulated 18.5  19.0  18.5  18.5  18.5  18.0  18.5  18.5 18.0  19.5  % NV Viscosity 62″   55″   52″   37″   38″   39″   41″  41″   41″   57″   (sec) Drop 1.5 0.1 68.8  0.2 25   34.6  62.1  24.9 0.4 11.8  Damage Δ (mA) Measured 44/77/101 18/82/102 45/102 13/10217/101 34/94/103 41/103 46/77/104 17/82/104 30/93/107 Tgs (° C.)Scalping % 68   80   97   93   99   91   88   80   74   90   Citric SW7   6   8   6   8   8   9   9   8   8   Blush

As indicated by the coating performance data included in Tables 3 and 4,the use of a multi-stage latex enabled a substantial reduction in thepolyether polymer level, with a corresponding increase in the acryliclevel together with preservation of certain important end useperformance attributes. Those attributes included flexibility asindicated by the low change in metal exposure values after drop damage,and comparable resistance to flavor scalping relative to the control(viz., Comparative Finish Example 5, and compare e.g., Finish Example13). Notably, flexibility comparable to the control was achieved inseveral of the Finish Examples even though the control resin systemcontained 49 wt. % percent polyether and 51 wt. % acrylic, whereas theFinish Example resins systems contained 20 to 35 wt. % polyether and 65to 80 wt. % acrylic. Surprisingly, good flexibility was achieved even inmany Finish Examples whose resin system contained as much as 80 wt. %acrylic. This result was significant because as discussed above,typically there is a tradeoff in conventional acrylic systems betweenflexibility and resistance to flavor scalping, especially for acrylicsmade without using styrene.

Additional multi-stage latex systems were also produced that weresimilar to those of Examples 10-19, but included small amounts ofmulti-ethylenically unsaturated monomers (e.g., 1,4-butanedioldimethacrylate) in one or both of the higher Tg and lower Tg stages. Itwas observed (data not shown) that the inclusion of suchmulti-ethylenically monomers could improve both the corrosion resistanceand blush resistance of inside spray beverage can coatings formulatedfrom the resins systems, while not negatively impacting either theadvantageous drop damage resistance or flavor scalping resistanceproperties of the coating. Such beneficial properties were observed, forexample, for resin systems that included about 2.5 to about 5 weightpercent of multi-ethylenically unsaturated monomers (e.g.,1,4-butanediol dimethacrylate), based on the weight ofmulti-ethylenically unsaturated monomer relative to the total weight ofmonomers used to generate all of the emulsion polymerized stages (e.g.,the aggregate weight of the monomers used to form the lower and high Tgstages).

Example 20 Gradient Tg Latex Made with Low Molecular Weight Surfactant

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen, 318.6 parts deionized water and 9.6parts RHODAPON UB (29-30% active sodium lauryl sulfate, CAS No.68585-47-7, commercially available from Solvay) are added. Withagitation on and the vessel blanketed with inert gas, the mixture isheated to 80° C. In a separate vessel, a mixture of 52.8 parts deionizedwater, 4.2 parts RHODAPON UB, 119.4 parts butyl methacrylate, 29.9 partsbutyl acrylate, 14.9 parts methyl methacrylate and 1.7 parts methacrylicacid is prepared. The monomers used are butyl methacrylate/butylacrylate/methyl methacrylate/methacrylic acid at a weight ratio of72/18/9/1 with a Fox equation calculated Tg of 9.6° C. This mixturerepresents polymerizable monomer pre-emulsion 1 (ME-1). In a secondvessel, a mixture of 71.3 parts deionized water, 5.4 parts RHODAPON UB,21.7 parts butyl methacrylate, 10.9 parts butyl acrylate, 171.6 partsmethyl methacrylate, 19.7 parts 2-hydroxyethyl methacrylate (HEMA) and2.2 parts methacrylic acid is prepared. The monomers used are butylmethacrylate/butyl acrylate/methyl methacrylate/HEMA/methacrylic acid ata weight ratio of 10/5/75.2/8.8/1 with a Fox equation calculated Tg of78.0° C. This mixture represents polymerizable monomer pre-emulsion 2(ME-2), and its HEMA content facilitates film crosslinking using asuitable crosslinker (e.g., phenolic or melamine resins). When thereactor temperature reaches 80° C., 1.9 parts ammonium persulfatedissolved in 50 parts deionized water are added. After a 5 minute hold,ME-1 is fed directly into the reactor over 240 minutes. Concurrently,ME-2 is fed into the ME-1 vessel over 225 minutes. After 240 minutes, 40parts deionized water is used to rinse the remaining contents of theME-1 and ME-2 vessels into the reactor. The batch is held for 30additional minutes while cooling to about 70° C. Once the batchtemperature reaches about 70° C., a solution of 0.95 parts tert-butylhydroperoxide in 25 parts deionized water is added followed immediatelyby addition of a solution of 0.43 parts erythorbic acid dissolved in 25parts deionized water. The batch is held at temperature for 30 minutesand then cooled. Once the batch cools to <40° C., sufficientdimethylamino ethanol is added to raise the pH to about 8.0. The latexis filtered through a 100 micron filter bag. The resultant gradient Tglatex should contain about 40% solids and have a pH of about 8.

Example 21 Gradient Tg Latex Made with Low Molecular Weight Surfactant

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen, 318.0 parts deionized water and 10.0parts RHODAPON UB are added. With agitation on and the vessel blanketedwith inert gas, the mixture is heated to 80° C. In a separate vessel, amixture of 55.2 parts deionized water, 4.3 parts RHODAPON UB, 125.0parts butyl methacrylate, 31.3 parts butyl acrylate, 11.9 parts methylmethacrylate, 3.9 parts HEMA and 1.7 parts methacrylic acid is prepared.The monomers used are butyl methacrylate/butyl acrylate/methylmethacrylate/HEMA/methacrylic acid at a weight ratio of 72/18/6.8/2.2/1with a Fox equation calculated Tg of 8.9° C. This mixture representspolymerizable monomer pre-emulsion 1 (ME-1). In a second vessel, amixture of 72.2 parts deionized water, 5.7 parts RHODAPON UB, 22.4 partsbutyl methacrylate, 11.4 parts butyl acrylate, 185.6 parts methylmethacrylate, 6.6 parts HEMA and 2.3 parts methacrylic acid is prepared.The monomers used are butyl methacrylate/butyl acrylate/methylmethacrylate/HEMA/methacrylic acid at a weight ratio of 10/5/81.2/2.8/1with a Fox equation calculated Tg of 81.0° C. This mixture representspolymerizable monomer pre-emulsion 2 (ME-2). When the reactortemperature reaches 80° C., 2.0 parts ammonium persulfate dissolved in50 parts deionized water are added. After a 5 minute hold, ME-1 is feddirectly into the reactor over 240 minutes. Concurrently, ME-2 is fedinto ME-1 vessel over 225 minutes. After 240 minutes, 40 parts deionizedwater is used to rinse the remaining content of the ME-1 and ME-2vessels into the reactor. The batch is held for 30 additional minuteswhile cooling to about 70° C. Once the batch temperature reaches about70° C., a solution of 0.97 parts tert-butyl hydroperoxide in 25 partsdeionized water is added followed immediately by addition of a solutionof 0.44 parts erythorbic acid dissolved in 25 parts deionized water. Thebatch is held at temperature for 30 minutes and then cooled. Once thebatch cools to <40° C., sufficient dimethylethanol amine is added toraise its pH to about 8.0. The latex is filtered through a 100 micronfilter bag. The resultant gradient Tg latex should contain about 40%solids and have a pH of about 8.

Example 22 Gradient Tg Latex Made with Water-Dispersible PolymericSurfactant

To a reactor equipped with an agitator, reflux condenser, andthermocouple, capable of being heated and cooled and blanketed orsparged with inert gas or nitrogen, 399.5 parts of the Example 4copolymer and 220.3 parts deionized water are added. With agitation onand the vessel blanketed with inert gas, the mixture is heated to 82° C.In a separate vessel a mixture of 65.15 parts butyl methacrylate, 16.29parts butyl acrylate, 9.05 parts methyl methacrylate and 0.75 partsbenzoin is prepared. The monomers used are butyl methacrylate/butylacrylate/methyl methacrylate at a weight ratio of 72/18/10 with a Foxequation calculated Tg of 9° C. This mixture represents stage 1polymerizable monomers. In another vessel an initiator solution isprepared by mixing 1.62 parts 34% hydrogen peroxide and 72 partsdeionized water. In yet another vessel a mixture of 11.87 parts butylmethacrylate, 5.87 parts butyl acrylate, 100.75 parts methylmethacrylate and 0.87 parts benzoin is prepared. The monomers used arebutyl methacrylate/butyl acrylate/methyl methacrylate at a weight ratioof 10/5/85 with a Fox equation calculated Tg of 82° C. This mixturerepresents stage 2 polymerizable monomers. When the reactor temperaturereaches 81° C., the stage 1 monomer mixture and the initiator solutionare fed separately into the reactor over 240 minutes. Concurrently, thestage 2 monomer mixture is fed into the stage 1 monomer mixture over 225minutes. After 240 minutes, 81.25 parts deionized water is used to rinseboth stage 1 and 2 monomer mixture vessels into the reactor. With thecontents of the reactor at 82° C., 0.12 parts benzoin and 0.12 parts 34%hydrogen peroxide are added and rinsed into the reactor with 7.37 partsdeionized water. The batch is held for 30 minutes and allowed toexotherm. After 30 minutes 0.12 parts benzoin and 0.12 parts 34%hydrogen peroxide are added and rinsed into the reactor with 7.37 partsdeionized water. The batch is held at temperature for one hour and thencooled. The resultant gradient Tg latex should contain about 30% solidsand have an acid number of about 36 mg KOH/g and 0.3 micrometer averageparticle size.

The invention is further disclosed in the following embodiments:

1. An aqueous coating composition comprising:

-   -   a multi-stage polymeric latex having two or more emulsion        polymerized stages, wherein the latex has one or both of: (i) a        lower Tg emulsion polymerized stage having a calculated Tg that        is at least 20° C., at least 30° C., at least 35° C., at least        40° C., at least 50° C., at least 60° C., or at least 70° C.        lower than a calculated Tg of a higher Tg emulsion polymerized        stage or (ii) a gradient Tg; with the proviso that if the latex        has (i), more than 50 weight percent of the emulsion polymerized        stages preferably have a calculated Tg of at least 40° C., at        least 50° C., at least 60° C., at least 70° C., or at least 80°        C.; and    -   an aqueous carrier liquid;    -   wherein the aqueous coating composition is a food or beverage        can coating composition.

2. An aqueous coating composition comprising:

-   -   a resin system including a water-dispersible polymer and two or        more emulsion polymerized stages of a multi-stage polymeric        latex; wherein the water-dispersible polymer is incorporated        into the multi-stage polymeric latex, blended with the        multi-stage polymeric latex, or both; and wherein the latex has        one or both of: (i) a lower Tg emulsion polymerized stage having        a calculated Tg that is at least 20° C., at least 30° C., at        least 35° C., at least 40° C., at least 50° C., at least 60° C.,        or at least 70° C. lower than a calculated Tg of a higher Tg        emulsion polymerized stage or (ii) a gradient Tg; and    -   an aqueous carrier liquid;    -   wherein the aqueous coating composition is a food or beverage        can coating composition.

3. The coating composition of embodiment 2, wherein monomers used toform the two or more emulsion polymerized stages are emulsionpolymerized in the presence of the water-dispersible polymer.

4. The coating composition of embodiment 2 or 3, wherein thewater-dispersible polymer comprises an acrylic polymer, a polyetherpolymer, a polyolefin polymer, a polyester polymer, a polyurethanepolymer, or a mixture or copolymer thereof.

5. An aqueous coating composition comprising:

-   -   a resin system including a multi-stage polymeric latex having        two or more emulsion polymerized stages, wherein the multi-stage        latex is formed by emulsion polymerizing ethylenically        unsaturated monomers in the presence of an aqueous dispersion of        a water-dispersible polymer, wherein:        -   the latex has one or both of: (i) a lower Tg emulsion            polymerized stage having a calculated Tg that is at least            20° C., at least 30° C., at least 35° C., at least 40° C.,            at least 50° C., at least 60° C., or at least 70° C. lower            than a calculated Tg of a higher Tg emulsion polymerized            stage or (ii) a gradient Tg, and            -   the water-dispersible polymer comprises a polyether                polymer; and    -   an aqueous carrier liquid;    -   wherein the aqueous coating composition is a food or beverage        can coating composition.

6. The coating composition of any of embodiments 2 to 5, with theproviso that if the latex has (i), more than 50 weight percent of theemulsion polymerized stages have a calculated Tg of at least 40° C., atleast 50° C., at least 60° C., at least 70° C., or at least 80° C.

7. An aqueous coating composition comprising:

-   -   a resin system including a multi-stage polymeric latex formed by        emulsion polymerizing ethylenically unsaturated monomers in two        or more stages (e.g., a lower Tg stage and a higher Tg stage) in        the presence of a water-dispersible polymer (e.g., a polyether        polymer), wherein the emulsion polymerized ethylenically        unsaturated monomers comprise at least 80 wt. % of two or more        (e.g., two, three, four, or five) of methyl methacrylate, ethyl        acrylate, ethyl methacrylate, butyl acrylate (e.g., n-butyl        acrylate), and butyl methacrylate (e.g., n-butyl methacrylate);        and    -   an aqueous carrier liquid;    -   wherein the coating composition is a food or beverage can        coating composition.

8. The coating composition of any of embodiments 2 to 7, wherein theresin system includes at least 60 wt. %, at least 65 wt. %, at least 70wt. %, at least 75 wt. %, or at least 80 wt. % of units derived fromethylenically unsaturated monomers, based on the combined weight of thewater-dispersible polymer and the monomers used to form the emulsionpolymerized stages.

9. The coating composition of any preceding embodiment, wherein thehigher Tg emulsion polymerized stage has a calculated Tg of greater than40° C. and the lower Tg emulsion polymerized stage has a calculated Tgof less than 40° C.

10. The coating composition of any preceding embodiment, wherein thehigher Tg emulsion polymerized stage has a calculated Tg of greater than45° C. and the lower Tg emulsion polymerized stage has a calculated Tgof less than 35° C.

11. The coating composition of any preceding embodiment, wherein thehigher Tg emulsion polymerized stage has a calculated Tg of greater than50° C. and the lower Tg emulsion polymerized stage has a calculated Tgof less than 30° C.

12. The coating composition of any preceding embodiment, wherein thehigher Tg emulsion polymerized stage has a calculated Tg of greater than60° C. and the lower Tg emulsion polymerized stage has a calculated Tgof less than 20° C.

13. The coating composition of any preceding embodiment, wherein thehigher Tg emulsion polymerized stage has a calculated Tg of greater than70° C. and the lower Tg emulsion polymerized stage has a calculated Tgof less than 10° C.

14. The coating composition of any preceding embodiment, wherein thelower Tg emulsion polymerized stage is emulsion polymerized before thehigher Tg emulsion polymerized stage.

15. The coating composition of any of embodiments 1 to 13, wherein thelower Tg emulsion polymerized stage is emulsion polymerized after thehigher Tg emulsion polymerized stage.

16. The coating composition of any of preceding embodiment, wherein theweight ratio of the lower Tg emulsion polymerized stage relative to thehigher Tg emulsion polymerized stage ranges from 5:95 to 95:5, from20:80 to 70:30, or from 25:75 to 48:52.

17. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the aggregate of monomers used to form the twoor more emulsion polymerized stages) include at least 30 wt. %, at least50 wt. %, at least 70 wt. %, at least 85 wt. %, or at least 95 wt. % (oreven 100 wt. %) of one or more (meth)acrylates.

18. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the aggregate of monomers used to form the twoor more emulsion polymerized stages) include at least 30 wt. %, at least50 wt. %, at least 70 wt. %, at least 85 wt. %, or at least 95 wt. % (oreven 100 wt. %) of one or more alkyl (meth)acrylates.

19. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the aggregate of monomers used to form the twoor more emulsion polymerized stages) include at least 30 wt. %, at least50 wt. %, at least 70 wt. %, at least 85 wt. %, or at least 95 wt. % ofone or more alkyl methacrylates.

20. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the aggregate of monomers used to form the twoor more emulsion polymerized stages) include at least 30 wt. %, at least35 wt. %, at least 40 wt. %, or at least 45 wt. %, or even 80 wt. % ormore of one or more ethylenically unsaturated monomers having acycloaliphatic group or a linear or branched hydrocarbon group includingat least 4 carbon atoms.

21. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the aggregate of the monomers used to form thetwo or more emulsion polymerized stages) include at least 20 wt. %, atleast 30 wt. %, at least 35 wt. %, at least 40 wt. %, or even 80 wt. %or more of one or more ethylenically unsaturated monomers having alinear or branched hydrocarbon group including at least 4 carbon atomsand having a longest chain length of at least 3 carbon atoms.

22. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the monomers used to form each of therespective two or more emulsion polymerized stages) include one or moreC1-C3 alkyl (meth)acrylates.

23. The coating composition of embodiment 22, wherein the one or moreC1-C3 alkyl (meth)acrylates comprise ethyl methacrylate, methylmethacrylate, or a combination thereof.

24. The coating composition of any of embodiments 20 to 23, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the monomers used to form each of two or morerespective two or more emulsion polymerized stages) include both the oneor more ethylenically unsaturated monomers having a cycloaliphatic groupor a linear or branched hydrocarbon group including at least 4 carbonatoms and the one or more C1-C3 alkyl (meth)acrylates.

25. The coating composition of any of embodiments 1 to 6 or 8 to 24,wherein the monomers used to form at least one of the emulsionpolymerized stages (and in some embodiments the aggregate of monomersused to form the two or more emulsion polymerized stages) include atleast 80 wt. % of one or more (e.g., one, two, three, four, or five) ofmethyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate(e.g., n-butyl acrylate), and butyl methacrylate (e.g., n-butylmethacrylate).

26. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stages(and in some embodiments the monomers used to form each of therespective two or more emulsion polymerized stages) include a butylmethacrylate, a butyl acrylate, or both.

27. The coating composition of embodiment 26, wherein the monomers usedto form the at least one emulsion polymerized stage, and in someembodiments the monomers used to form each of the respective two or moreemulsion polymerized stages, include both n-butyl methacrylate and oneor both of ethyl methacrylate or methyl methacrylate.

28. The coating composition of embodiment 27, wherein the monomers usedto form the at least one emulsion polymerized stage, and in someembodiments the monomers used to form each of the respective two or moreemulsion polymerized stages, further include one or more of ethylacrylate, methyl acrylate, or n-butyl acrylate.

29. The coating composition of any preceding embodiment, wherein themonomers used to form at least one of the emulsion polymerized stagesincludes a multi-ethylenically unsaturated monomer (e.g., amulti-ethylenically unsaturated (meth)acrylate).

30. The coating composition of any preceding embodiment, wherein thecoating composition is substantially free of, completely free of or doesnot contain each of bisphenol A, bisphenol F, and bisphenol S.

31. The coating composition of any preceding embodiment, wherein thecoating composition is not prepared using halogenated monomers, or issubstantially free of, completely free of or does not containhalogenated monomers.

32. The coating composition of any preceding embodiment, wherein thecoating composition is substantially free of, completely free of or doesnot contain styrene and optionally also is substantially free of,completely free of or does not contain substituted styrene compounds.

33. The coating composition of any preceding embodiment, wherein theresin system (and optionally the coating composition) is substantiallyfree of, completely free of or does not contain vinyl aromatic compounds

34. The coating composition of any preceding embodiment, wherein thecalculated Tg of the aggregate of monomers used to form the two or moreemulsion polymerized stages is at least 0° C., at least 20° C., at least30° C., at least 40° C., or at least 50° C.

35. The coating composition of any preceding embodiment, wherein themonomers used to form the lower Tg and higher Tg emulsion polymerizedstages (and optionally any additional optional emulsion polymerizedstages) do not include any monomers that do not have a homopolymer Tg.

36. The coating composition of any preceding embodiment, wherein themonomers used to form the lower Tg and higher Tg emulsion polymerizedstages include less than 5 weight percent, if any, of monomers that donot have a homopolymer Tg, based on the total weight of the monomersused to form the lower Tg and higher Tg stages.

37. The coating composition of any of embodiments 2 to 36, wherein theresin system consists essentially of the water-dispersible polymer andthe two or more emulsion polymerized ethylenically unsaturated monomers.

38. The coating composition of any preceding embodiment, wherein the twoor more emulsion polymerized stages consist essentially of the lower Tgand higher Tg emulsion polymerized stages.

39. The coating composition of any of embodiments 2 to 36, wherein thewater-dispersible polymer includes one or more neutralized acid or basegroups.

40. The coating composition of any of embodiments 2 to 39, wherein thewater-dispersible polymer includes one or more structural units derivedfrom ethylenically unsaturated monomer, more typically one or morestructural units derived from an acrylate or a methacrylate.

41. The coating composition of embodiment 40, wherein thewater-dispersible polymer includes one or more structural unit derivedfrom an acid- or anhydride-functional ethylenically unsaturated monomer.

42. The coating composition of any of embodiments 39 to 41, wherein thewater-dispersible polymer includes one or more ammonia-neutralized oramine-neutralized acid or anhydride groups.

43. The coating composition of any of embodiments 2 to 42, wherein theweight ratio of water-dispersible polymer to emulsion polymerized stagesis less than 50:50, less than 40:60, less than 30:70, less than 25:75,or less than 20:80.

44. The coating composition of any of embodiments 2 to 43, wherein thewater-dispersible polymer comprises a polyether polymer that has acalculated Tg of at least 60° C., at least 70° C., at least 80° C., orfrom 80 to 110° C.

45. The coating composition of any of embodiments 2 to 44, wherein thewater-dispersible polymer comprises an aromatic polyether polymer.

46. The coating composition of any of embodiments 2 to 45, wherein thewater-dispersible polymer has a number average molecular weight of atleast 2,000, at least 3,000, or at least 4,000.

47. The coating composition of any of embodiments 2 to 46, wherein thewater-dispersible polymer comprises an organic solution polymerizedpolymer.

48. The coating composition of any of embodiments 2 to 47, wherein thewater-dispersible polymer comprises a polyether polymer formed fromreactants including an extender and a diepoxide.

49. The coating composition of embodiment 48, wherein the diepoxidecomprises a diepoxide of a dihydric phenol.

50. The coating composition of embodiment 49, wherein the dihydricphenol comprises an ortho-substituted dihydric phenol.

51. The coating composition of embodiment 50, wherein the diepoxide ofan ortho-substituted dihydric phenol comprises a diepoxide oftetramethyl bisphenol F (e.g., a diglycidyl ether of tetramethylbisphenol F).

52. The coating composition of embodiment 50, wherein the diepoxide ofan ortho-substituted dihydric phenol comprises a diepoxide of2,2′-biphenol or other bridged dihydric phenol having a ring to ringbridge linkage located ortho to a phenol oxygen atom.

53. The coating composition of embodiment 48, wherein the diepoxidecomprises a diepoxide of an aromatic diol (e.g., benzene dimethanol,vanillyl alcohol, furan dimethanol, and the like), an aromatic diacid(e.g., isophthalic acid, terephthalic acid, and the like), an aliphaticdiol, an aliphatic diacid, a cycloaliphatic diol (e.g., cyclobutanediols such as 2,2,4,4-tetramethyl-1,3-cyclobutanediol), a cycloaliphaticdiacid (e.g., cyclobutane diacids such as2,2,4,4-tetramethyl-1,3-cyclobutane dicarboxylic acid), or a combinationthereof.

54. The coating composition of any of embodiments 48 to 53, wherein theextender comprises a dihydric phenol.

55. The coating composition of embodiment 54, wherein the extendercomprises a dihydric monophenol.

56. The coating composition of embodiment 55, wherein the dihydricmonophenol comprises hydroquinone.

57. The coating composition of embodiment 54, wherein the extendercomprises 2,2′-biphenol or other bridged dihydric phenol having a ringto ring bridge linkage located ortho to a phenol oxygen atom.

58. The coating composition of any of embodiments 2 to 50 and 53 to 56,wherein the water-dispersible polymer (and optionally the coatingcomposition) is substantially free of, completely free of or does notcontain any structural units derived from a bisphenol.

59. The coating composition of any of embodiments 2 to 58, wherein thewater-dispersible polymer comprises a copolymer that includes both apolyether polymer and a vinyl addition component.

60. The coating composition of embodiment 59, wherein thewater-dispersible polymer comprises a polyether-acrylate copolymer.

61. The coating composition of embodiment 59 or 60, wherein the vinyladdition component is formed from a monomer mixture that includes both(i) a (meth)acrylic acid and (ii) a (meth)acrylate.

62. The coating composition of embodiment 60 or 61, wherein thepolyether-acrylate copolymer comprises the reaction product of anoxirane-functional polyether polymer reacted with an acid- oranhydride-functional acrylate polymer in the presence of a tertiaryamine.

63. The coating composition of any of embodiments 60 to 62, wherein apolyether polymer used to form the polyether-acrylate copolymercomprises from 30 to 95 wt. % of the polyether-acrylate copolymer.

64. The coating composition of any of embodiments 2 to 63, wherein thewater-dispersible polymer has an acid number from 40 to 200 mg KOH pergram.

65. The coating composition of any of embodiments 2 to 64, wherein thewater-dispersible polymer includes secondary hydroxyl groups.

66. The coating composition of any of embodiments 2 to 65, wherein thewater-dispersible polymer includes —CH₂CH(OH)CH₂— segments.

67. The coating composition of any preceding embodiment, wherein thecoating composition is substantially free of, completely free of or doesnot contain each of bisphenol A, bisphenol F, and bisphenol S.

68. The coating composition of any preceding embodiment, wherein thecoating composition has a viscosity of from 20 to 80 seconds (Ford Cup#2, 25° C.) and is an inside spray coating composition for a food orbeverage can.

69. The coating composition of any preceding embodiment, wherein thecoating composition, when spray applied onto an interior of a 355 mL no.211 drawn & ironed aluminum beverage can at a dry film weight of 115milligrams per can and cured at 188° C. to 199° C. (measured at the candome) for 55 seconds, exhibits a lower sidewall adhesion rating value of9 or 10 after retort in 2% citric acid under pressure at 121° C. andtested according to ASTM D 3359—Test Method B, using SCOTCH 610 tape,available from 3M Company of Saint Paul, Minn.

70. The coating composition of any preceding embodiment, wherein thecoating composition, when spray applied onto an interior of a 355 mL no.211 drawn & ironed aluminum beverage can at a dry film weight of 115milligrams per can and cured at 188° C. to 199° C. (measured at the candome) for 55 seconds, exhibits a contact angle with deionized watergreater than about 80, more preferably greater than about 85, and evenmore preferably greater than about 90.

71. The coating composition of any preceding embodiment, wherein theresin system comprises at least 10 wt. %, at least 20 wt. %, at least 50wt. %, at least 75 wt. %, at least 90 wt. %, or at least 99 wt. % of thecoating composition, based on the combined weight of thewater-dispersible polymer and the two or more emulsion polymerizedstages relative to the total weight of the resin solids in the coatingcomposition.

72. The coating composition of any preceding embodiment, wherein thecoating composition includes a crosslinker.

73. The coating composition of embodiment 72, wherein the crosslinkercomprises a phenoplast.

74. The coating composition of any preceding embodiment, wherein theaqueous carrier liquid comprises at least 50 wt. % water.

75. The coating composition of any preceding embodiment, wherein thecoating composition comprises from 5 wt. % to 40 wt. % of solids, moretypically from 10 wt. % to 30 wt. % of solids, and from 15 wt. % to 25wt. % of solids.

76. The coating composition of any preceding embodiment, wherein thecoating compositions includes, based on total resin solids, at least 50wt. % of the two or more emulsion polymerized stages.

77. The coating composition of any of embodiments 2 to 76, wherein thecoating composition includes, based on total resin solids, at least 50wt. %, at least 75 wt. %, at least 90 wt. %, or at least 95 wt. % of thewater-dispersible polymer and the two or more emulsion polymerizedstages, based on the combined weight of the water-dispersible polymerand the two or more emulsion polymerized stages.

78. The coating composition of any of embodiments 2 to 77, wherein thetotal amount of polymerized ethylenically unsaturated monomers comprisemore than 50 wt. %, preferably more than 60 wt. %, even more preferablymore than 70 wt. %, and optimally 80 wt. % or more of the total resinsolids of the coating composition.

79. The coating composition of embodiment 78, where the emulsionpolymerized monomers of the higher Tg and lower Tg comprise at least 50wt. %, at least 60 wt. %, at least 75 wt. %, or at least 85 wt. % ormore of the total amount of polymerized ethylenically unsaturatedmonomers present in the coating composition.

80. The coating composition of any of embodiments 2 to 79, whereinpolymerized ethylenically unsaturated monomers comprise at least 60 wt.%, at least 65 wt. %, at least 70 wt. %, at least 75 wt. %, or at least80 wt. % of the total combined weight of water-dispersible polymer andpolymerized ethylenically unsaturated monomers.

81. The coating composition of any preceding embodiment, wherein whenthe coating composition, when spray applied onto an interior of a 355 mLno. 211 two-piece drawn and ironed aluminum beverage can at 115milligrams per can coating weight and cured at 188° C. to 199° C.(measured at the can dome) for 55 seconds, gives a metal exposure ofless than 3.5 mA when tested pursuant to the Metal Exposure after DropDamage test disclosed herein.

82. The coating composition of any preceding embodiment, wherein whenthe coating composition, when spray applied onto an interior of a 355 mLno. 211 two-piece drawn and ironed aluminum beverage can at 115milligrams per can coating weight and cured at 188° C. to 199° C.(measured at the can dome) for 55 seconds, is capable of passing anecking and flanging test as indicated by a change of metal exposureafter necking of less than 1.0 mA, more preferably a change of less 0.1mA, and even more preferably no measurable change.

83. A food or beverage can, or a portion thereof, having a cured coatingformed from the coating composition of any preceding embodiment disposedon at least a portion of a metal substrate.

84. The food or beverage can, or a portion thereof, of embodiment 83,wherein the overall average dry coating film weight is from 1.0 to 6.5grams per square meter.

85. The food or beverage can, or a portion thereof, of embodiment 83 or84, wherein the metal substrate has an average thickness from 125 to 635micrometers.

86. The food or beverage can, or a portion thereof, of any ofembodiments 82 to 84 wherein the coating is an interior food-contactcoating of an aluminum beverage can.

87. The food or beverage can of any of embodiments 83 to 86, wherein thecured coating exhibits a contact angle with deionized water greater thanabout 80, more preferably greater than about 85, and even morepreferably greater than about 90.

88. The food or beverage can of any of embodiments 83 to 87 containing apackaged food or beverage product.

89. A method of coating a food or beverage can comprising applying thecoating composition of any of embodiments 1 to 82 to a surface of ametal substrate prior to or after forming the metal substrate into afood or beverage can or a portion thereof.

90. The method of embodiment 89 wherein the coating composition is sprayapplied onto an interior surface of a can including a sidewall bodyportion and end portion.

91. The method of embodiment 89 or 90, wherein the can is an aluminumbeverage can.

92. The multi-stage polymeric latex of embodiment 1 or resin system ofany of embodiments 2 to 81.

93. A method of making a latex dispersion that is substantially free of,completely free of or does not contain each of bisphenol A, bisphenol F,and bisphenol S, and is also optionally substantially free of,completely free of or does not contain styrene, the method comprising:

-   -   providing an aqueous dispersion of a water-dispersible polymer        (e.g., a water-dispersible polymer of any preceding embodiment);        and    -   emulsion polymerizing two or more stages in the presence of the        aqueous dispersion to form a multi-stage polymeric latex,        wherein the latex has one or both of: (i) a lower Tg emulsion        polymerized stage having a calculated Tg that is preferably at        least 20° C., at least 30° C., at least 35° C., at least 40° C.,        at least 50° C., at least 60° C., or at least 70° C. lower than        a calculated Tg of a higher Tg emulsion polymerized stage        or (ii) a gradient Tg.

94. The method of embodiment 93, wherein the water-dispersible polymercomprises a polyether polymer.

95. The method of embodiment 93, wherein the polyether polymer comprisesan aromatic polyether polymer having base-neutralized acid groups,acid-neutralized base groups, or a combination thereof.

96. The method of any of embodiments 93 to 95, wherein the weight ratioof water-dispersible polymer to emulsion polymerized stages is less than50:50, less than 40:60, less than 30:70, less than 25:75, or less than20:80.

97. The method of any of embodiments 93 to 95, wherein polymerizedethylenically unsaturated monomers comprise at least 60 wt. %, at least65 wt. %, at least 70 wt. %, at least 75 wt. %, or at least 80 wt. % ofthe total combined weight of water-dispersible polymer and polymerizedethylenically unsaturated monomers.

98. The method of any of embodiments 93 to 97, wherein the lower Tgemulsion polymerized stage is emulsion polymerized before the higher Tgemulsion polymerized stage.

99. The method of any of embodiments 93 to 97, wherein the lower Tgemulsion polymerized stage is emulsion polymerized after the higher Tgemulsion polymerized stage.

100. The latex dispersion resulting from any of embodiments 93 to 99.

101. The coating composition, can, method, polymeric latex or latexdispersion of any preceding embodiment, wherein the emulsion polymerizedethylenically unsaturated monomer component, and more preferably theentire latex, includes or is derived from no more than 0.5 wt. %, andmore preferably no more than 0.1 wt. % of low molecular weightsurfactants based on the aggregate weight of the ethylenicallyunsaturated monomer component and polymerizable monomers employed tomake the latex.

102. The coating composition, can, method, polymeric latex or latexdispersion of any of embodiments 1 to 100, wherein the emulsionpolymerized ethylenically unsaturated monomer component, and morepreferably the entire latex, is derived using primarily or only lowmolecular weight surfactants.

103. The coating composition, can, method, polymeric latex or latexdispersion of any preceding embodiment, wherein the emulsion polymerizedethylenically unsaturated monomer component, and more preferably theentire latex, is also or instead emulsion polymerized in the presence ofone or more polymerizable surfactants.

104. The coating composition, can, method, polymeric latex or latexdispersion of any preceding claim, wherein the emulsion polymerizedethylenically unsaturated monomer component, and more preferably theentire latex, includes or is derived from no more than 0.5 wt. %, andmore preferably no more than 0.1 wt. % of acrylamide-type monomers basedon the aggregate weight of the ethylenically unsaturated monomercomponent and polymerizable monomers employed to make the latex.

The complete disclosure of all patents, patent applications, andpublications (including material safety data sheets, technical datasheets and product brochures for the raw materials and ingredients usedin the Examples), and electronically available material cited herein areincorporated herein by reference as if individually incorporated. Theforegoing detailed description and examples have been given for clarityof understanding only. No unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for variations obvious to one skilled in the art will beincluded within the invention defined by the embodiments. The inventionillustratively disclosed herein suitably may be practiced, in someembodiments, in the absence of any element which is not specificallydisclosed herein.

The invention claimed is:
 1. An article comprising an aluminum or steeltwo-piece drawn and ironed food or beverage can, having an interiorspray-applied liquid or hardened coating formed from an aqueous coatingcomposition comprising: a multi-stage polymeric latex having two or moreemulsion polymerized ethylenically unsaturated monomer stages in anaqueous carrier liquid, wherein the latex has one or both of: (i) alower Tg emulsion polymerized stage having a calculated Tg that is atleast 20° C. lower than a calculated Tg of a higher Tg emulsionpolymerized stage, wherein more than 50 weight percent of the emulsionpolymerized stages have a calculated Tg of greater than 40° C. and thelower Tg emulsion polymerized stage has a calculated Tg of less than 40°C. and wherein the emulsion polymerized stages include or are derivedfrom no more than 0.5 wt. % of acrylamide-type monomers, if any, basedon the aggregate weight of ethylenically unsaturated monomers employedto make the emulsion polymerized stages, or (ii) a gradient Tg using avarying charge of two or more monomers with at least a 20° C.differential in the calculated Tg of monomers fed at the start ofpolymerization compared to monomers fed at the end of polymerization;wherein at least one of the emulsion polymerized stages is formed frommonomers including at least 80 wt. % of one or more of methylmethacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, andbutyl methacrylate; and wherein the coating when hardened exhibits:(iii) a global extraction result of less than 50 ppm; and (iv) a metalexposure of less than 3 mA on average when the can is filled with 1%NaCl in deionized water and tested pursuant to the Initial MetalExposure test method disclosed herein.
 2. The article of claim 1,wherein the latex has a lower Tg emulsion polymerized stage having acalculated Tg that is at least 20° C. lower than a calculated Tg of ahigher Tg emulsion polymerized stage, wherein more than 50 weightpercent of the emulsion polymerized stages have a calculated Tg ofgreater than 40° C. and the lower Tg emulsion polymerized stage has acalculated Tg of less than 40° C. and wherein the emulsion polymerizedstages include or are derived from no more than 0.5 wt. % ofacrylamide-type monomers, if any, based on the aggregate weight ofethylenically unsaturated monomers employed to make the emulsionpolymerized stage.
 3. The article of claim 2, wherein the latex has alower Tg emulsion polymerized stage having a calculated Tg of less than30° C. and a higher Tg emulsion polymerized stage having a calculated Tgof greater than 50° C.
 4. The article of claim 2, wherein the latex hasa lower Tg emulsion polymerized stage having a calculated Tg of lessthan 20° C. and a higher Tg emulsion polymerized stage having acalculated Tg of greater than 60° C.
 5. The article of claim 2, whereinthe latex has a lower Tg emulsion polymerized stage having a calculatedTg that is at least 40° C. lower than a calculated Tg of the higher Tgemulsion polymerized stage.
 6. The article of claim 2, wherein the latexhas a lower Tg emulsion polymerized stage having a calculated Tg that isat least 60° C. lower than a calculated Tg of the higher Tg emulsionpolymerized stage.
 7. The article of claim 2, wherein more than 50weight percent of the emulsion polymerized stages have a calculated Tgof at least 60° C.
 8. The article of claim 2, wherein two or more of theemulsion polymerized stages are formed from monomers having in theaggregate a calculated Tg of at least 30° C.
 9. The article of claim 2,wherein the aqueous coating composition includes, based on total resinsolids, at least 50 wt. % of the two or more emulsion polymerizedstages.
 10. The article of claim 2, wherein the aqueous coatingcomposition contains more than 70 wt. % resin solids from polymerizedethylenically unsaturated monomers based on total resin solids in thecoating composition.
 11. The article of claim 2, wherein at least 50 wt.% of the (meth)acrylates present in the monomers used to form one ormore of the emulsion polymerized stages are methacrylates.
 12. Thearticle of claim 2, wherein at least one of the emulsion polymerizedstages is formed from monomers including a multi-ethylenicallyunsaturated monomer.
 13. The article of claim 2, wherein the coatingcomposition is substantially free of each of bisphenol A, bisphenol F,and bisphenol S, the coating composition is not prepared usinghalogenated monomers, and the coating composition includes or is derivedfrom no more than 0.5 wt. % of acrylamide-type monomers, if any, basedon the aggregate weight of the ethylenically unsaturated monomercomponent and polymerizable monomers employed to make the latex.
 14. Thearticle of claim 2, wherein the coating composition is substantiallyfree of styrene and substituted styrene compounds.
 15. The article ofclaim 2, wherein the coating composition includes or is derived from nomore than 10 wt. % polyether compounds or polymers based on the totalcoating composition solids.
 16. The article of claim 2, wherein theaqueous coating composition further comprises a crosslinker.
 17. Thearticle of claim 2, wherein the aqueous coating composition furthercomprises a phenoplast crosslinker.
 18. The article of claim 2, whereinthe aqueous coating composition has a viscosity of from 20 to 80 seconds(Ford Cup #2, 25° C.).
 19. The article of claim 2, wherein the coatingwhen hardened exhibits a lower sidewall adhesion rating value of 9 or 10after retort in 2% citric acid under pressure at 121° C. and testingaccording to ASTM D 3359—Test Method B.
 20. The article of claim 2,wherein the coating when hardened exhibits a metal exposure of less than3.5 mA when tested pursuant to the Metal Exposure after Drop Damage testdisclosed herein.
 21. The article of claim 2, wherein the coating whenhardened is capable of passing a necking and flanging test as indicatedby a change of metal exposure after necking of less than 1.0 mA.
 22. Thearticle of claim 2, wherein the coating composition is hardened and ison an interior food-contact coating of an aluminum beverage can.
 23. Thearticle of claim 2, wherein the coating composition is hardened and thecontainer further comprises a packaged food or beverage product.
 24. Thearticle of claim 2, wherein the aqueous coating composition furthercomprises a beta-hydroxyalkyl-amide crosslinker.
 25. The article ofclaim 2, wherein the lower Tg emulsion polymerized stage was emulsionpolymerized before the higher Tg emulsion polymerized stage.
 26. Thearticle of claim 2, wherein the lower Tg emulsion polymerized stage wasemulsion polymerized after the higher Tg emulsion polymerized stage. 27.The article of claim 2, wherein the weight ratio of the lower Tgemulsion polymerized stage relative to the higher Tg emulsionpolymerized stage ranges from 25:75 to 48:52.
 28. The article of claim1, wherein the latex has a gradient Tg.
 29. An article comprising analuminum or steel two-piece drawn and ironed food or beverage can,having an interior spray-applied liquid or hardened coating formed froman aqueous coating composition comprising: a multi-stage polymeric latexhaving two or more emulsion polymerized ethylenically unsaturatedmonomer stages in an aqueous carrier liquid, wherein the latex has agradient Tg using a varying charge of two or more monomers with at leasta 20° C. differential in the calculated Tg of monomers fed at the startof polymerization compared to monomers fed at the end of polymerization;and wherein the coating when hardened exhibits: (i) a global extractionresult of less than 50 ppm; and (ii) a metal exposure of less than 3 mAon average when the can is filled with 1% NaCl in deionized water andtested pursuant to the Initial Metal Exposure test method disclosedherein.
 30. The article of claim 29, wherein more than 50 weight percentof the emulsion polymerized stages have a calculated Tg of at least 60°C.
 31. The article of claim 29, wherein two or more of the emulsionpolymerized stages are formed from monomers having in the aggregate acalculated Tg of at least 30° C.
 32. The article of claim 29, whereinthe aqueous coating composition includes, based on total resin solids,at least 50 wt. % of the two or more emulsion polymerized stages. 33.The article of claim 29, wherein the aqueous coating compositioncontains more than 70 wt. % resin solids from polymerized ethylenicallyunsaturated monomers based on total resin solids in the coatingcomposition.
 34. The article of claim 29, wherein at least one of theemulsion polymerized stages is formed from monomers including at least50 wt. % of one or more (meth)acrylates.
 35. The article of claim 29,wherein at least one of the emulsion polymerized stages is formed frommonomers including a multi-ethylenically unsaturated monomer.
 36. Thearticle of claim 29, wherein the coating composition is substantiallyfree of each of bisphenol A, bisphenol F, and bisphenol S, the coatingcomposition is not prepared using halogenated monomers, and the coatingcomposition includes or is derived from no more than 0.5 wt. % ofacrylamide-type monomers, if any, based on the aggregate weight of theethylenically unsaturated monomer component and polymerizable monomersemployed to make the latex.
 37. The article of claim 29, wherein thecoating composition is substantially free of styrene and substitutedstyrene compounds.
 38. The article of claim 29, wherein the coatingcomposition includes or is derived from no more than 10 wt. % polyethercompounds or polymers based on the total coating composition solids. 39.The article of claim 29, wherein the aqueous coating composition furthercomprises a crosslinker.
 40. The article of claim 29, wherein theaqueous coating composition further comprises a phenoplast crosslinker.41. The article of claim 29, wherein the aqueous coating composition hasa viscosity of from 20 to 80 seconds (Ford Cup #2, 25° C.).
 42. Thearticle of claim 29, wherein the interior spray-applied coating whenhardened exhibits a lower sidewall adhesion rating value of 9 or 10after retort in 2% citric acid under pressure at 121° C. and testingaccording to ASTM D 3359 —Test Method B.
 43. The article of claim 29,wherein the interior spray-applied coating when hardened exhibits ametal exposure of less than 3.5 mA when tested pursuant to the MetalExposure after Drop Damage test disclosed herein.
 44. The article ofclaim 29, wherein the interior spray-applied coating when hardened iscapable of passing a necking and flanging test as indicated by a changeof metal exposure after necking of less than 1.0 mA.
 45. The article ofclaim 29, wherein the food or beverage can further comprises a packagedfood or beverage product.
 46. The article of claim 29, wherein theaqueous coating composition further comprises a beta-hydroxyalkyl-amidecrosslinker.
 47. The article of claim 29, wherein the lower Tg emulsionpolymerized stage was emulsion polymerized before the higher Tg emulsionpolymerized stage.
 48. The article of claim 29, wherein the lower Tgemulsion polymerized stage was emulsion polymerized after the higher Tgemulsion polymerized stage.
 49. The article of claim 29, wherein theweight ratio of the lower Tg emulsion polymerized stage relative to thehigher Tg emulsion polymerized stage ranges from 25:75 to 48:52.
 50. Anarticle comprising an aluminum or steel two-piece drawn and ironed foodor beverage can, having an interior spray-applied liquid or hardenedcoating formed from an aqueous coating composition comprising: amulti-stage polymeric latex having two or more emulsion polymerizedethylenically unsaturated monomer stages in an aqueous carrier liquid,wherein the latex has one or both of: (i) a lower Tg emulsionpolymerized stage having a calculated Tg that is at least 20° C. lowerthan a calculated Tg of a higher Tg emulsion polymerized stage, whereinmore than 50 weight percent of the emulsion polymerized stages have acalculated Tg of greater than 40° C. and the lower Tg emulsionpolymerized stage has a calculated Tg of less than 40° C. and whereinthe emulsion polymerized stages include or are derived from no more than0.5 wt. % of acrylamide-type monomers, if any, based on the aggregateweight of ethylenically unsaturated monomers employed to make theemulsion polymerized stages, or (ii) a gradient Tg using a varyingcharge of two or more monomers with at least a 20° C. differential inthe calculated Tg of monomers fed at the start of polymerizationcompared to monomers fed at the end of polymerization; wherein theaqueous coating composition further comprises a beta-hydroxyalkyl-amidecrosslinker; and wherein the coating when hardened exhibits: (iii) aglobal extraction result of less than 50 ppm; and (iv) a metal exposureof less than 3 mA on average when the can is filled with 1% NaCl indeionized water and tested pursuant to the Initial Metal Exposure testmethod disclosed herein.
 51. The article of claim 50, wherein the latexhas a lower Tg emulsion polymerized stage having a calculated Tg of lessthan 30° C. and a higher Tg emulsion polymerized stage having acalculated Tg of greater than 50° C.
 52. The article of claim 50,wherein the latex has a lower Tg emulsion polymerized stage having acalculated Tg of less than 20° C. and a higher Tg emulsion polymerizedstage having a calculated Tg of greater than 60° C.
 53. The article ofclaim 50, wherein the latex has a lower Tg emulsion polymerized stagehaving a calculated Tg that is at least 40° C. lower than a calculatedTg of the higher Tg emulsion polymerized stage.
 54. The article of claim50, wherein the latex has a lower Tg emulsion polymerized stage having acalculated Tg that is at least 60° C. lower than a calculated Tg of thehigher Tg emulsion polymerized stage.
 55. The article of claim 50,wherein more than 50 weight percent of the emulsion polymerized stageshave a calculated Tg of at least 60° C.
 56. The article of claim 50,wherein two or more of the emulsion polymerized stages are formed frommonomers having in the aggregate a calculated Tg of at least 30° C. 57.The article of claim 50, wherein the aqueous coating compositionincludes, based on total resin solids, at least 50 wt. % of the two ormore emulsion polymerized stages.
 58. The article of claim 50, whereinthe aqueous coating composition contains more than 70 wt. % resin solidsfrom polymerized ethylenically unsaturated monomers based on total resinsolids in the coating composition.
 59. The article of claim 50, whereinat least one of the emulsion polymerized stages is formed from monomersincluding at least 50 wt. % of one or more (meth)acrylates.
 60. Thearticle of claim 50, wherein at least one of the emulsion polymerizedstages is formed from monomers including a multi-ethylenicallyunsaturated monomer.
 61. The article of claim 50, wherein the coatingcomposition is substantially free of each of bisphenol A, bisphenol F,and bisphenol S, the coating composition is not prepared usinghalogenated monomers, and the coating composition includes or is derivedfrom no more than 0.5 wt. % of acrylamide-type monomers, if any, basedon the aggregate weight of the ethylenically unsaturated monomercomponent and polymerizable monomers employed to make the latex.
 62. Thearticle of claim 50, wherein the coating composition is substantiallyfree of styrene and substituted styrene compounds.
 63. The article ofclaim 50, wherein the coating composition includes or is derived from nomore than 10 wt. % polyether compounds or polymers based on the totalcoating composition solids.
 64. The article of claim 50, wherein theaqueous coating composition has a viscosity of from 20 to 80 seconds(Ford Cup #2, 25° C.).
 65. The article of claim 50, wherein the interiorspray-applied coating when hardened exhibits a lower sidewall adhesionrating value of 9 or 10 after retort in 2% citric acid under pressure at121° C. and testing according to ASTM D 3359—Test Method B.
 66. Thearticle of claim 50, wherein the interior spray-applied coating whenhardened exhibits a metal exposure of less than 3.5 mA when testedpursuant to the Metal Exposure after Drop Damage test disclosed herein.67. The article of claim 50, wherein the interior spray-applied coatingwhen hardened is capable of passing a necking and flanging test asindicated by a change of metal exposure after necking of less than 1.0mA.
 68. The article of claim 50, wherein the container further comprisesa packaged food or beverage product.
 69. The article of claim 50,wherein the lower Tg emulsion polymerized stage was emulsion polymerizedbefore the higher Tg emulsion polymerized stage.
 70. The article ofclaim 50, wherein the lower Tg emulsion polymerized stage was emulsionpolymerized after the higher Tg emulsion polymerized stage.
 71. Thearticle of claim 50, wherein the weight ratio of the lower Tg emulsionpolymerized stage relative to the higher Tg emulsion polymerized stageranges from 25:75 to 48:52.
 72. A method for making a coated food orbeverage container or container component, the method comprising thesteps of: (a) spray applying on an interior surface of an aluminum orsteel two-piece drawn and ironed food or beverage can having a bodyportion and an end portion an aqueous coating composition comprising amulti-stage polymeric latex having two or more emulsion polymerizedstages in an aqueous carrier liquid, wherein the latex has one or bothof: (i) a lower Tg emulsion polymerized stage having a calculated Tgthat is at least 20° C. lower than a calculated Tg of a higher Tgemulsion polymerized stage, wherein more than 50 weight percent of theemulsion polymerized stages have a calculated Tg of greater than 40° C.and the lower Tg emulsion polymerized stage has a calculated Tg of lessthan 40° C. and wherein the emulsion polymerized stages include or arederived from no more than 0.5 wt. % of acrylamide-type monomers based,if any, on the aggregate weight of ethylenically unsaturated monomersemployed to make the emulsion polymerized stages, or (ii) a gradient Tgusing a varying charge of two or more monomers with at least a 20° C.differential in the calculated Tg of monomers fed at the start ofpolymerization compared to monomers fed at the end of polymerization;wherein at least one of the emulsion polymerized stages is formed frommonomers including at least 80 wt. % of one or more of methylmethacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, andbutyl methacrylate; and (b) curing the coating composition to form ahardened coating; wherein the hardened coating exhibits: (iii) a globalextraction result of less than 50 ppm; and (iv) a metal exposure of lessthan 3 mA on average when the can is filled with 1% NaCl in deionizedwater and tested pursuant to the Initial Metal Exposure test methoddisclosed herein.
 73. A method for making a coated food or beveragecontainer or container component, the method comprising the steps of:(a) spray applying on an interior surface of an aluminum or steeltwo-piece drawn and ironed food or beverage can having a body portionand an end portion an aqueous coating composition comprising amulti-stage polymeric latex having two or more emulsion polymerizedethylenically unsaturated monomer stages in an aqueous carrier liquid,wherein the latex has a gradient Tg using a varying charge of two ormore monomers with at least a 20° C. differential in the calculated Tgof monomers fed at the start of polymerization compared to monomers fedat the end of polymerization; and (b) curing the coating composition toform a hardened coating; wherein the hardened coating exhibits: (i) aglobal extraction result of less than 50 ppm; and (ii) a metal exposureof less than 3 mA on average when the can is filled with 1% NaCl indeionized water and tested pursuant to the Initial Metal Exposure testmethod disclosed herein.
 74. A method for making a coated food orbeverage container or container component, the method comprising thesteps of: (a) spray applying on an interior surface of an aluminum orsteel two-piece drawn and ironed food or beverage can having a bodyportion and an end portion an aqueous coating composition comprising amulti-stage polymeric latex having two or more emulsion polymerizedstages in an aqueous carrier liquid, wherein the latex has one or bothof: (i) a lower Tg emulsion polymerized stage having a calculated Tgthat is at least 20° C. lower than a calculated Tg of a higher Tgemulsion polymerized stage, wherein more than 50 weight percent of theemulsion polymerized stages have a calculated Tg of greater than 40° C.and the lower Tg emulsion polymerized stage has a calculated Tg of lessthan 40° C. and wherein the emulsion polymerized stages include or arederived from no more than 0.5 wt. % of acrylamide-type monomers, if any,based on the aggregate weight of ethylenically unsaturated monomersemployed to make the emulsion polymerized stages, or (ii) a gradient Tgusing a varying charge of two or more monomers with at least a 20° C.differential in the calculated Tg of monomers fed at the start ofpolymerization compared to monomers fed at the end of polymerization;wherein the aqueous coating composition further comprises abeta-hydroxyalkyl-amide crosslinker; and (b) curing the coatingcomposition to form a hardened coating; wherein the hardened coatingexhibits: (iii) a global extraction result of less than 50 ppm; and (iv)a metal exposure of less than 3 mA on average when the can is filledwith 1% NaCl in deionized water and tested pursuant to the Initial MetalExposure test method disclosed herein.